Method and apparatus for supporting light connection in next generation mobile communication systems

ABSTRACT

The present disclosure relates to a communication technique for converging a 5G communication system, which is provided to support a higher data transmission rate beyond a 4G system with an IoT technology, and a system therefor. The present disclosure may be applied to intelligent services (e.g., smart home, smart building, smart city, smart car or connected car, health care, digital education, retail business, security and safety related service, or the like) based on the 5G communication technology and the IoT related technology. The present disclosure discloses a method and an apparatus for supporting a multiple access in next generation mobile communication systems.

PRIORITY

This application claims priority under 35 U.S.C. § 119(a) to KoreanPatent Application Serial No. 10-2017-0000623, which was filed in theKorean Intellectual Property Office on Jan. 3, 2017, the entire contentof which is hereby incorporated herein by reference.

BACKGROUND 1. Field of the Disclosure

The present disclosure relates generally to a method and an apparatusfor supporting a multiple access in next generation mobile communicationsystems, and more particularly, to a method and apparatus for supportinglight connection in next generation mobile communication systems.

2. Description of the Related Art

The 5G communication system or the pre-5G communication system is calleda beyond 4G network communication system or a post LTE system. Toachieve a high data transmission rate, the 5G communication system isconsidered to be implemented in a very high frequency (mmWave) band(e.g., like 60 GHz band).

To relieve a path loss of a radio wave and increase a transfer distanceof the radio wave in the very high frequency band, in the 5Gcommunication system, beamforming, massive multiple-input andmultiple-output (MIMO), full dimensional MIMO (FD-MIMO), array antenna,analog beam-forming, and large scale antenna technologies have beenused. To improve a network of the system, in the 5G communicationsystem, technologies such as an evolved small cell, an advanced smallcell, a cloud radio access network (cloud RAN), an ultra-dense network,a device to device communication (D2D), a wireless backhaul, a movingnetwork, cooperative communication, coordinated multi-points (CoMP), andreception interference cancellation have been developed.

In addition, in the 5G system, hybrid frequency-shift keying (FSK) andquadrature amplitude modulation (QAM) modulation (FQAM) and slidingwindow superposition coding (SWSC) that are an advanced codingmodulation (ACM) scheme and a filter bank multi carrier (FBMC), anonorthogonal multiple access (NOMA), and a sparse code multiple access(SCMA) that are an advanced access technology, and so on have beendeveloped.

The Internet has evolved from a human-centered connection networkthrough which a human being generates and consumes information to theInternet of things (IoT) network that transmits/receives informationbetween distributed components such as things and processes theinformation. The Internet of everything (IoE) technology in which bigdata processing technology is combined with the IoT technology byconnection with a cloud server has also emerged. To implement the IoT,technology elements, such as a sensing technology, wired and wirelesscommunication and network infrastructure, a service interfacetechnology, and a security technology, have been used. Recently,technologies such as a sensor network, machine to machine (M2M), andmachine type communication (MTC) for connecting between things have beenused. In the IoT environment, an intelligent Internet technology (IT)service that creates a new value in human life by collecting andanalyzing data generated in the connected things may be provided. TheIoT may apply for fields, such as a smart home, a smart building, asmart city, a smart car or a connected car, a smart grid, health care,smart appliances, and an advanced healthcare service, by fusing andcombining the existing information technology with various industries.

Therefore, 5G communication systems has been applied to the IoT network.The 5G communication technologies, such as the sensor network, the M2M,and the MTC, have been used by techniques such as the beamforming, theMIMO, and the array antenna. The application of the cloud RAN as the bigdata processing technology described above may also be used forcombining the 5G communication technology with the IoT technology.

In the next generation mobile communication systems, when a terminalusing a light connection releases a connection with a network and triesto reconnect with the network after a predetermined time, there is aneed to identify a base station (or cell) that supports the lightconnection and a base station (or cell) that does not support the lightconnection. When the light connection to the base station (or cell) thatdoes not support the light connection is resumed, a normal connectioncannot be established.

SUMMARY

In the next generation mobile communication systems, if only onesequence number (SN) is used, it is possible to reduce overhead uponsupporting a single connection. However, it is impossible to support amultiple access with one SN. Therefore, a new mechanism needs to beadded. Accordingly, an aspect of the present disclosure provides a gapencoding method, and a radio link control (RLC) status reporting methodthat supports a loss of a large number of packets.

In the next generation mobile communication systems, when the expirationdate of the data packet expires, processing the expired packet is animportant issue. The expired packet may already be a packet dataconvergence protocol (PDCP) protocol data unit (PDU), or may be an RLCPDU or a media access control (MAC) PDU. That is, functions of eachlayer may be affected depending on how to process the expired packet.Accordingly, an aspect of the present disclosure provides differentprocessing methods depending on an extent that the expired packet isprocessed.

Accordingly, an aspect of the present disclosure provides a method forenabling a terminal to identify whether or not to support a lightconnection and establish a connection by broadcasting system informationas to whether each base station supports a light connection in nextgeneration mobile communication systems.

In the current LTE system, when a terminal performs a handover (HO), theterminal performs synchronization based on a random access procedure toa target cell, and receives an uplink grant to complete a handoverprocedure. If a handover without a random access procedure is introducedto reduce the influence of time interference in the handover procedure,there is no way to inform the successful completion of the handoverprocedure. Accordingly, an aspect of the present disclosure provides amethod for determining successful completion of a handover with a targetcell when a terminal performs handover without a random access.

When an LTE terminal supporting vehicle to everything (V2X) has alimited RF chain, there is a problem as to which link should be selectedif an uplink transmission link to a base station and a side linktransmission between the V2X terminals are generated at the same time.Accordingly, an aspect of the present disclosure provides a clearpriority and operation principle of an uplink transmission link to abase station for an LTE terminal supporting V2X and a side linktransmission between V2X terminals.

In accordance with an aspect of the present disclosure, there is providea method by a terminal in a wireless communication system. The methodincludes receiving, from a source base station, a message indicating ahandover without random access from the source base station to a targetbase station, receiving, on a downlink control channel from the targetbase station, an uplink grant for the handover, and transmitting, to thetarget base station, a message indicating a completion of the handoverbased on the uplink grant.

In accordance with an aspect of the present disclosure, there is providea method by a target base station in a wireless communication system.The method includes receiving, from a source base station, a message torequest a handover without random access for a terminal, transmitting,on a downlink control channel to the terminal, an uplink grant for thehandover without random access, and receiving, from the terminal, amessage indicating a completion of the handover without random accessbased on the uplink grant.

In accordance with an aspect of the present disclosure, there isprovided a terminal in a wireless communication system. The terminalincludes transceiver and a controller coupled with the transceiver andconfigured to control the transceiver to: receive, from a source basestation, a message indicating a handover without random access from thesource base station to a target base station, receive, on a downlinkcontrol channel from the target base station, an uplink grant for thehandover, and transmit, to the target base station, a message indicatinga completion of the handover based on the uplink grant.

In accordance with an aspect of the present disclosure, there isprovided a target base station in a wireless communication system. Thetarget base station includes a transceiver and a controller coupled withthe transceiver and configured to control the transceiver to: receive,from a source base station, a message to request a handover withoutrandom access for a terminal, transmit, on a downlink control channel tothe terminal, an uplink grant for the handover, and receive, from theterminal, a message indicating a completion of the handover based on theuplink grant.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of the presentdisclosure will be more apparent from the following detaileddescription, taken in conjunction with the accompanying drawings, inwhich:

FIG. 1A is a diagram of a long term evolution (LTE) system, according toan embodiment of the present disclosure;

FIG. 1B is a diagram of a radio protocol structure in the LTE system,according to an embodiment of the present disclosure;

FIG. 1C is a diagram of a structure of a next generation mobilecommunication system, according to an embodiment of the presentdisclosure;

FIG. 1D is a diagram of a radio protocol structure of a next generationmobile communication system proposed in the present disclosure,according to an embodiment of the present disclosure;

FIG. 1E is a diagram of setting, by a terminal, each layer apparatus inthe next generation mobile communication system, according to anembodiment of the present disclosure;

FIGS. 1FA and 1FB are diagrams of a terminal for receiving servicesthrough an LTE base station and an NR base station in the nextgeneration mobile communication system, according to an embodiment ofthe present disclosure;

FIGS. 1GA and 1GB are diagrams of when one SN is used in a multipleaccess environment, according to an embodiment of the presentdisclosure;

FIG. 1H is a diagram of a multiple access that is supported by one SN,according to an embodiment of the present disclosure;

FIG. 1I is a diagram of a multiple access that is supported by one SN,according to an embodiment of the present disclosure;

FIG. 1J is a diagram of a multiple access that is supported by one SN,according to an embodiment of the present disclosure;

FIG. 1K is a diagram of a multiple access that is supported by one SN,according to an embodiment of the present disclosure;

FIG. 1L is a diagram of a multiple access that is supported by one SN,according to an embodiment of the present disclosure;

FIG. 1M is a diagram of an RLC status reporting method, according to anembodiment of the present disclosure;

FIG. 1N is a diagram of an RLC status reporting method, according to anembodiment of the present disclosure;

FIG. 1O is a diagram of an RLC status reporting method, according to anembodiment of the present disclosure;

FIG. 1P is a diagram of an RLC status reporting method, according to anembodiment of the present disclosure;

FIG. 1Q is a flowchart of an operation of a terminal, according to anembodiment of the present disclosure;

FIG. 1R is a block diagram of an internal structure of the terminal,according to an embodiment of the present disclosure;

FIG. 1S is a block diagram of a base station transceiver, according toan embodiment of the present disclosure;

FIG. 2A is a diagram of a structure of an LTE system, according to anembodiment of the present disclosure;

FIG. 2B is a diagram of a radio protocol structure in the LTE system,according to an embodiment of the present disclosure;

FIG. 2C is a diagram of a next generation mobile communication system,according to an embodiment of the present disclosure;

FIG. 2D is a diagram of a radio protocol structure of a next generationmobile communication system, according to an embodiment of the presentdisclosure;

FIGS. 2EA and 2EB are diagrams of a terminal for receiving servicesthrough an LTE base station and a new radio (NR) base station in thenext generation mobile communication system, according to an embodimentof the present disclosure;

FIG. 2F is a diagram of a method for processing a data packet inadvance, according to an embodiment of the present disclosure;

FIG. 2G is a diagram of a timer (e.g., PDCP discard timer) maintained ata PDCP layer, according to an embodiment of the present disclosure;

FIGS. 2HA, 2HB, and 2HC are diagrams of an expiring packet, according toan embodiment of the present disclosure;

FIGS. 2IA and 2IB are flowcharts for a method of a terminal, accordingto an embodiment of the present disclosure;

FIG. 2J is a flow for a method of a terminal of a receiving end,according to an embodiment of the present disclosure;

FIGS. 2KA and 2KB are diagrams of an expiring packet, according to anembodiment of the present disclosure;

FIG. 2L is a flowchart for a method of a terminal, according to anembodiment of the present disclosure;

FIG. 2M is a diagram of a PDCP control PDU that processes an expiringpacket, according to an embodiment of the present disclosure;

FIG. 2N is a diagram of setting, by a terminal, each layer apparatus inthe next generation mobile communication, according to an embodiment ofthe present disclosure;

FIG. 2O is a block diagram of an internal structure of the terminal,according to an embodiment of the present disclosure;

FIG. 2P is a block diagram of a base station transceiver, according toan embodiment of the present disclosure;

FIG. 3A is a diagram of an LTE system, according to an embodiment of thepresent disclosure;

FIG. 3B is a diagram of a radio protocol structure in the LTE system,according to an embodiment of the present disclosure;

FIG. 3C is a diagram of a next generation mobile communication system,according to an embodiment of the present disclosure;

FIG. 3D is a diagram of a radio protocol structure of a next generationmobile communication system, according to an embodiment of the presentdisclosure;

FIG. 3E is a diagram of a light connection concept, according to anembodiment of the present disclosure;

FIG. 3F is a diagram of a method for establishing a connection of ageneral terminal to a network so that the general terminaltransmits/receives data, according to an embodiment of the presentdisclosure;

FIG. 3G is a diagram of updating, by a general terminal, a trackingregion, according to an embodiment of the present disclosure;

FIG. 3H is a diagram of a light connection procedure of a terminal and abase station for supporting a light connection in a next generationmobile communication system, according to an embodiment of the presentdisclosure;

FIG. 3I is a diagram of a method for a paging area update (PAU) to a newbase station by the light connected terminal, according to an embodimentof the present disclosure;

FIG. 3J is a diagram of a method for a PAU to a new base station by thelight connected terminal, according to an embodiment of the presentdisclosure;

FIG. 3K is a diagram of a method for a PAU to a new base station by thelight connected terminal, according to an embodiment of the presentdisclosure;

FIG. 3L is a flowchart for a method of a terminal when the lightconnected mode terminal establishes an RRC connection to the network,according to an embodiment of the present disclosure;

FIG. 3M is a diagram of the terminal when the light connected modeterminal performs the PAU, according to an embodiment of the presentdisclosure;

FIG. 3N is a block diagram of the terminal, according to an embodimentof the present disclosure;

FIG. 3O is a block diagram of a base station transceiver, according toan embodiment of the present disclosure;

FIG. 4A is a diagram of the network structure of the wirelesscommunication system, according to an embodiment of the presentdisclosure;

FIG. 4B is a diagram of a radio protocol structure in an LTE system,according to an embodiment of the present disclosure;

FIG. 4C is a diagram of a method for performing a handover in theexisting LTE system, according to an embodiment of the presentdisclosure;

FIG. 4D is a diagram of a method for performing a random access channel(RACH)-less handover, according to an embodiment of the presentdisclosure;

FIG. 4E is a diagram of a method for performing a RACH-less handover,according to an embodiment of the present disclosure;

FIG. 4F is a diagram of a PDCCH structure corresponding to mgs4 in asecond operation, according to an embodiment of the present disclosure;

FIG. 4G is a flowchart for a method of a terminal of performing aRACH-less handover, according to an embodiment of the presentdisclosure;

FIG. 4H is a block diagram of the terminal, according to an embodimentof the present disclosure;

FIG. 4I is a block diagram of a base station, mobility management entity(MME), and serving-gateway (S-GW), according to an embodiment of thepresent disclosure;

FIG. 5A is a diagram of the LTE system, according to an embodiment ofthe present disclosure;

FIG. 5B is a diagram of a radio protocol structure in the LTE system,according to an embodiment of the present disclosure;

FIG. 5C is a diagram of a V2X communication within a cellular system,according to an embodiment of the present disclosure;

FIG. 5D is a diagram of a method for a data transmission procedure of aV2X terminal operated in a mode 3, according to an embodiment of thepresent disclosure;

FIG. 5E is a diagram of a method for a data transmission of a V2Xterminal operated in a mode 4, according to an embodiment of the presentdisclosure;

FIG. 5F is a diagram of a first operation of the terminal according topriority of Uu and PC5, according to an embodiment of the presentdisclosure;

FIG. 5G is a diagram of a first operation of the terminal according topriority of Uu and PC5, according to an embodiment of the presentdisclosure;

FIG. 5H is a block diagram of the terminal, according to an embodimentof the present disclosure; and

FIG. 5I is a block diagram of the base station, according to anembodiment of the present disclosure.

DETAILED DESCRIPTION

Embodiments of the present disclosure will be described herein belowwith reference to the accompanying drawings. However, the embodiments ofthe present disclosure are not limited to the specific embodiments andshould be construed as including all modifications, changes, equivalentdevices and methods, and/or alternative embodiments of the presentdisclosure. In the description of the drawings, similar referencenumerals are used for similar elements.

The terms “have,” “may have,” “include,” and “may include” as usedherein indicate the presence of corresponding features (for example,elements such as numerical values, functions, operations, or parts), anddo not preclude the presence of additional features.

The terms “A or B,” “at least one of A or/and B,” or “one or more of Aor/and B” as used herein include all possible combinations of itemsenumerated with them. For example, “A or B,” “at least one of A and B,”or “at least one of A or B” means (1) including at least one A, (2)including at least one B, or (3) including both at least one A and atleast one B.

The terms such as “first” and “second” as used herein may modify variouselements regardless of an order and/or importance of the correspondingelements, and do not limit the corresponding elements. These terms maybe used for the purpose of distinguishing one element from anotherelement. For example, a first user device and a second user device mayindicate different user devices regardless of the order or importance.For example, a first element may be referred to as a second elementwithout departing from the scope the present invention, and similarly, asecond element may be referred to as a first element.

It will be understood that, when an element (for example, a firstelement) is “(operatively or communicatively) coupled with/to” or“connected to” another element (for example, a second element), theelement may be directly coupled with/to another element, and there maybe an intervening element (for example, a third element) between theelement and another element. To the contrary, it will be understoodthat, when an element (for example, a first element) is “directlycoupled with/to” or “directly connected to” another element (forexample, a second element), there is no intervening element (forexample, a third element) between the element and another element.

The expression “configured to (or set to)” as used herein may be usedinterchangeably with “suitable for,” “having the capacity to,” “designedto,” “adapted to,” “made to,” or “capable of” according to a context.The term “configured to (set to)” does not necessarily mean“specifically designed to” in a hardware level. Instead, the expression“apparatus configured to . . . ” may mean that the apparatus is “capableof . . . ” along with other devices or parts in a certain context. Forexample, “a processor configured to (set to) perform A, B, and C” maymean a dedicated processor (e.g., an embedded processor) for performinga corresponding operation, or a generic-purpose processor (e.g., acentral processing unit (CPU) or an application processor (AP)) capableof performing a corresponding operation by executing one or moresoftware programs stored in a memory device.

The terms used in describing the various embodiments of the presentdisclosure are for the purpose of describing particular embodiments andare not intended to limit the present disclosure. As used herein, thesingular forms are intended to include the plural forms as well, unlessthe context clearly indicates otherwise. All of the terms used hereinincluding technical or scientific terms have the same meanings as thosegenerally understood by an ordinary skilled person in the related artunless they are defined otherwise. The terms defined in a generally useddictionary should be interpreted as having the same or similar meaningsas the contextual meanings of the relevant technology and should not beinterpreted as having ideal or exaggerated meanings unless they areclearly defined herein. According to circumstances, even the termsdefined in this disclosure should not be interpreted as excluding theembodiments of the present disclosure.

The term “module” as used herein may, for example, mean a unit includingone of hardware, software, and firmware or a combination of two or moreof them. The “module” may be interchangeably used with, for example, theterm “unit”, “logic”, “logical block”, “component”, or “circuit”. The“module” may be a minimum unit of an integrated component element or apart thereof. The “module” may be a minimum unit for performing one ormore functions or a part thereof. The “module” may be mechanically orelectronically implemented. For example, the “module” according to thepresent invention may include at least one of an application-specificintegrated circuit (ASIC) chip, a field-programmable gate arrays (FPGA),and a programmable-logic device for performing operations which has beenknown or are to be developed hereinafter.

An electronic device according to the present disclosure may include atleast one of, for example, a smart phone, a tablet personal computer(PC), a mobile phone, a video phone, an electronic book reader (e-bookreader), a desktop PC, a laptop PC, a netbook computer, a workstation, aserver, a personal digital assistant (PDA), a portable multimedia player(PMP), a MPEG-1 audio layer-3 (MP3) player, a mobile medical device, acamera, and a wearable device. The wearable device may include at leastone of an accessory type (e.g., a watch, a ring, a bracelet, an anklet,a necklace, a glasses, a contact lens, or a head-mounted device (HMD)),a fabric or clothing integrated type (e.g., an electronic clothing), abody-mounted type (e.g., a skin pad, or tattoo), and a bio-implantabletype (e.g., an implantable circuit).

The electronic device may be a home appliance. The home appliance mayinclude at least one of, for example, a television, a digital video disk(DVD) player, an audio, a refrigerator, an air conditioner, a vacuumcleaner, an oven, a microwave oven, a washing machine, an air cleaner, aset-top box, a home automation control panel, a security control panel,a TV box (e.g., Samsung HomeSync™, Apple TV™, or Google TV™), a gameconsole (e.g., Xbox™ and PlayStation™), an electronic dictionary, anelectronic key, a camcorder, and an electronic photo frame.

The electronic device may include at least one of various medicaldevices (e.g., various portable medical measuring devices (a bloodglucose monitoring device, a heart rate monitoring device, a bloodpressure measuring device, a body temperature measuring device, etc.), amagnetic resonance angiography (MRA), a magnetic resonance imaging(MRI), a computed tomography (CT) machine, and an ultrasonic machine), anavigation device, a global positioning system (GPS) receiver, an eventdata recorder (EDR), a flight data recorder (FDR), a vehicleinfotainment device, an electronic device for a ship (e.g., a navigationdevice for a ship, and a gyro-compass), avionics, security devices, anautomotive head unit, a robot for home or industry, an automatic tellermachine (A™) in banks, point of sales (POS) devices in a shop, or an IoTdevice (e.g., a light bulb, various sensors, electric or gas meter, asprinkler device, a fire alarm, a thermostat, a streetlamp, a toaster, asporting goods, a hot water tank, a heater, a boiler, etc.).

The electronic device may include at least one of a part of furniture ora building/structure, an electronic board, an electronic signaturereceiving device, a projector, and various kinds of measuringinstruments (e.g., a water meter, an electric meter, a gas meter, and aradio wave meter). The electronic device may be a combination of one ormore of the aforementioned various devices. The electronic device mayalso be a flexible device. Further, the electronic device is not limitedto the aforementioned devices, and may include an electronic deviceaccording to the development of new technology.

Hereinafter, an electronic device according to various embodiments willbe described with reference to the accompanying drawings. In the presentdisclosure, the term “user” may indicate a person using an electronicdevice or a device (e.g., an artificial intelligence electronic device)using an electronic device.

The present disclosure discloses a method of a terminal includingidentifying missed RLC PDUs based on a SN of a plurality of RLC PDUsreceived from a base station; generating a message including a firstfield indicating the number of missed RLC PDUs and a second fieldindicating whether there is the first field; and transmitting a messagefrom the base station.

The present disclosure discloses a method of a base station includingtransmitting a plurality of RLC PDUs to a terminal; and receiving, fromthe terminal, a message including a first field indicating the number ofmissed RLC PDUs among the plurality of RLC PDUs and a second fieldindicating whether there is the first field.

The present disclosure discloses a terminal including a transceiverconfigured to transmit/receive a signal; and a controller configured toidentify missed RLC PDUs based on a SN of a plurality of RLC PDUsreceived from a base station, generate a message including a first fieldindicating the number of missed RLC PDUs and a second field indicatingwhether there is the first field, and transmit the message to the basestation.

The present disclosure discloses a base station including a transceiverconfigured to transmit/receive a signal; and a controller configured totransmit a plurality of RLC PDUs to a terminal and receive, from aterminal, a message including a first field indicating the number ofmissed RLC PDUs among the plurality of RLC PDUs and a second fieldindicating whether there is the first field.

The present disclosure discloses a method of a terminal includingreceiving a PDCP service data unit (SDU) in PDCP entity; generating aPDCP PDU including a PDCP header for the PDCP SDU if a timercorresponding to the PDCP SDU expires; and transmitting the PDCP PDU toa base station.

The present disclosure discloses a method of a base station includingreceiving a PDCP PDU from a terminal; identifying whether the PDCP PDUincludes only a PDCP header; and performing decoding on the PDCP PDUbased on whether the PDCP PDU includes only the PDCP header, wherein ifthe PDCP PDU includes only the PDCP header, the decoding on the PDCP PDUmay be omitted.

The present disclosure discloses a terminal including a transceiverconfigured to transmit/receive a signal; and a controller configured toreceive a PDCP SDU in PDCP entity, generate a PDCP PDU including a PDCPheader for the PDCP SDU if a timer corresponding to the PDCP SDUexpires, and transmit the PDCP PDU to a base station.

The present disclosure discloses a method of a base station including atransceiver configured to transmit/receive a signal and a controllerconfigured to receive a PDCP PDU from a terminal, identify whether thePDCP PDU includes only a PDCP header, and perform decoding on the PDCPPDU based on whether the PDCP PDU includes only the PDCP header, whereinif the PDCP PDU includes only the PDCP header, the decoding on the PDCPPDU may be omitted.

The present disclosure discloses a method of a terminal includingreceiving, from a base station, information indicating whether the basestation supports a radio resource control (RRC) inactive mode; andtransmitting a message requesting a PAU to the base station when thebase station supports the RRC inactive mode.

The present disclosure discloses a method of a base station includingtransmitting information indicating whether the base station supports anRRC inactive mode to a terminal which is an RRC connected mode; andreceiving a message requesting a paging area update from the terminalwhen the base station supports the RRC inactive mode.

The present disclosure discloses a terminal including a transceiverconfigured to transmit/receive a signal; and a controller configured toreceive, from a base station, information indicating whether the basestation supports an RRC inactive mode and transmit a message requestinga paging area update to the base station if the base station supportsthe RRC inactive mode.

The present disclosure discloses a base station including a transceiverconfigured to transmit/receive a signal; and a controller configured toreceive, from a base station, information indicating whether the basestation supports an RRC inactive mode to a terminal which is an RRCconnected mode, and receive a message requesting a paging area updatefrom a terminal if the base station supports the RRC inactive mode.

The present disclosure discloses a method of a terminal includingreceiving, from a source base station, a message indicating a handoverwithout random access from the source base station to a target basestation; receiving, on a downlink control channel from the target basestation, an uplink grant for the handover without random access; andtransmitting, to the target base station, a message indicating acompletion of the handover without random access based on the uplinkgrant.

The present disclosure discloses a method of a base station includingreceiving, from a source base station, a message to request a handoverwithout random access for a terminal; transmitting, on a downlinkcontrol channel to the terminal, an uplink grant for the handoverwithout random access; and receiving, from the terminal, a messageindicating a completion of the handover without random access based onthe uplink grant.

The present disclosure discloses a terminal including a transceiverconfigured to transmit and receive signals; and a controller coupledwith the transceiver and configured to control the transceiver toreceive, from a source base station, a message indicating a handoverwithout random access from the source base station to a target basestation, receive, on a downlink control channel from the target basestation, an uplink grant for the handover without random access, andtransmit, to the target base station, a message indicating a completionof the handover without random access based on the uplink grant.

The present disclosure discloses a base station including a transceiverconfigured to transmit and receive signals; and a controller coupledwith the transceiver and configured to control the transceiver toreceive, from a source base station, a message to request a handoverwithout random access for a terminal, transmit, on a downlink controlchannel to the terminal, an uplink grant for the handover without randomaccess, and receive, from the terminal, a message indicating acompletion of the handover without random access based on the uplinkgrant.

The present disclosure discloses a method of a terminal includingidentifying a generation of an uplink data to be transmitted to a basestation and a generation of a side link data to be transmitted to anopponent terminal of device to device (D2D) communication; determiningthat the uplink data or the side link data are transmitted if thetransmission of the uplink data and the transmission of the side linkdata overlap with each other; and transmitting determined data among theside link data.

The present disclosure discloses a terminal including a transceiverconfigured to transmit/receive a signal; a controller configured toidentify a generation of an uplink data to be transmitted to a basestation and a generation of a side link data to be transmitted to anopponent terminal of D2D communication; determine that the uplink dataor the side link data are transmitted if the transmission of the uplinkdata and the transmission of the side link data overlap with each other;and transmit determined data among the side link data.

According to an aspect of the present disclosure, the overhead can bereduced by proposing the gap encoding method supporting multipleaccesses with one SN, and when a large number of packets are lost, thenew RLC status report method can be applied to reduce the overhead.

According to an aspect of the present disclosure, there is an effect ofpreventing a problem from occurring in each layer by proposing differentprocessing methods depending on to what extent the expired packet isprocessed when the expired packet is processed.

According to an aspect of the present disclosure, the terminal to whichthe light connection is applied confirms whether the light connection issupported by the base station (or cell) which can be currently connectedto system information and tries to establish the connection.

According to an aspect of the present disclosure, the method fordetermining a completion of successful handover with a target cell isdefined when the terminal performs handover without the random access,thereby completing the handover without affecting the time interferencein the handover procedure.

According to an aspect of the present disclosure, there is an effect ofclarifying how to operate when the transmission of different links isgenerated at the same time by proposing the clear prioritization andoperation principle of the uplink and downlink transmission link to thebase station for the LTE terminal supporting the V2X and the side linkbetween the V2X terminals.

Hereinafter, for convenience of explanation, the present disclosure usesterms and names defined in the 3rd generation partnership project longterm evolution (3GPP LTE). However, the present disclosure is notlimited to these terms and names but may also be identically applied tothe system according to other standards.

FIG. 1A is a diagram of an LTE system, according to an embodiment of thepresent disclosure.

As illustrated in FIG. 1A, a RAN of an LTE system is configured toinclude next generation base stations (evolved node B, hereinafter, ENB,Node B, or base station) 1 a-05, 1 a-10, 1 a-15, and 1 a-20, an MME 1a-25, and an S-GW 1 a-30. User equipment (hereinafter, UE or terminal) 1a-35 accesses an external network through the ENBs 1 a-05 to 1 a-20 andthe S-GW 1 a-30.

In FIG. 1A, the ENBs 1 a-05 to 1 a-20 correspond to an existing node Bof the universal mobile telecommunications system (UMTS). The ENB isconnected to the UE 1 a-35 through a radio channel and performs a morecomplicated role than an existing node B. In the LTE system, in additionto a real-time service like a voice over internet protocol (VoIP)through the Internet protocol, all the user traffics are served througha shared channel, and therefore an apparatus for collecting andscheduling status information such as a buffer status, an availabletransmission power status, and a channel state of the terminals isrequired. Here, the ENBs 1 a-05 to 1 a-20 control collecting andscheduling status information. One ENB generally controls a plurality ofcells. For example, to implement a transmission rate of 100 Mbps, theLTE system uses, as a radio access technology (RAT), orthogonalfrequency division multiplexing (OFDM) in, for example, a bandwidth of20 MHz. Further, an adaptive modulation & coding (AMC) scheme fordetermining a modulation scheme and a channel coding rate depending on achannel status of the terminal is applied. The S-GW 1 a-30 is anapparatus for providing a data bearer and generates or removes the databearer according to the control of the MME 1 a-25. The MME is anapparatus for performing a mobility management function for the terminaland various control functions and is connected to a plurality of basestations.

FIG. 1B is a diagram of a radio protocol structure in the LTE system.

Referring to FIG. 1B, the radio protocol of the LTE system is configuredto include PDCPs 1 b-05 and 1 b-40, RLCs 1 b-10 and 1 b-35, and MACs 1b-15 and 1 b-30 in the terminal and the ENB. The PDCPs 1 b-05 and 1 b-40control operations such as internet provider (IP) headercompression/decompression. The main functions of the PDCP are summarizedas follows.

Header compression and decompression function (Header compression anddecompression: robust header compression (ROHC) only)

Transfer of user data

In-sequence delivery function (In-sequence delivery of upper layer PDUsat PDCP re-establishment procedure for RLC acknowledgement mode (AM))

Reordering function (For split bearers in dual connectivity (DC) (onlysupport for RLC AM): PDCP PDU routing for transmission and PDCP PDUreordering for reception)

Duplicate detection function (Duplicate detection of lower layer servicedata unit (SDU)s at PDCP re-establishment procedure for RLC AM)

Retransmission function (Retransmission of PDCP SDUs at handover (HO)and, for split bearers in DC, of PDCP PDUs at PDCP data-recoveryprocedure, for RLC AM)

Ciphering and deciphering function (Ciphering and deciphering)

Timer-based SDU discard function (Timer-based SDU discard in uplink)

The RLCs 1 b-10 and 1 b-35 reconfigures the PDCP PDU to an appropriatesize to perform the automatic repeat request (ARQ) operation or thelike. The main functions of the RLC are summarized as follows.

Data transfer function (Transfer of upper layer PDUs)

ARQ function (Error Correction through ARQ (only for AM data transfer))

Concatenation, segmentation, reassembly functions (Concatenation,segmentation and reassembly of RLC SDUs (only for unacknowledged mode(UM) and AM data transfer))

Re-segmentation function (Re-segmentation of RLC data PDUs (only for AMdata transfer))

Reordering function (Reordering of RLC data PDUs (only for UM and AMdata transfer))

Duplicate detection function (Duplicate detection (only for UM and AMdata transfer))

Error detection function (Protocol error detection (only for AM datatransfer))

RLC SDU discard function (RLC SDU discard (only for UM and AM datatransfer))

RLC re-establishment function (RLC re-establishment)

The MACs 1 b-15 and 1 b-30 are connected to several RLC layerapparatuses configured in one terminal and perform an operation ofmultiplexing RLC PDUs into an MAC PDU and demultiplexing the RLC PDUsfrom the MAC PDU. The main functions of the MAC are summarized asfollows.

Mapping function (Mapping between logical channels and transportchannels)

Multiplexing/demultiplexing function (Multiplexing/demultiplexing of MACSDUs belonging to one or different logical channels into/from transportblocks (TB) delivered to/from the physical layer on transport channels)

Scheduling information reporting function (Scheduling informationreporting)

Hybrid automatic repeat request (HARQ) function (Error correctionthrough HARQ)

Priority handling function between logical channels (Priority handlingbetween logical channels of one UE)

Priority handling function between terminals (Priority handling betweenUEs by dynamic scheduling)

Multimedia broadcast multicast service (MBMS) identification function(MBMS identification)

Transport format selection function (Transport format selection)

Padding function (Padding)

Physical layers 1 b-20 and 1 b-25 perform channel-coding and modulatinghigher layer data, making the higher layer data as an OFDM symbol andtransmitting them to a radio channel, or demodulating andchannel-decoding the OFDM symbol received through the radio channel andtransmitting the demodulated and channel-decoded OFDM symbol to thehigher layer.

FIG. 1C is a diagram of a next generation mobile communication system,according to an embodiment of the present disclosure.

Referring to FIG. 1C, a RAN of a next generation mobile communicationsystem (hereinafter referred to as new radio (NR) or 5G) is configuredto include a next generation base station (NR node B, hereinafter NR gNBor NR base station) 1 c-10 and a NR core network (NR CN) 1 c-05. Theuser terminal (NR UE or UE) 1 c-15 accesses the external network throughthe NR gNB 1 c-10 and the NR CN 1 c-05.

In FIG. 1C, the NR gNB 1 c-10 corresponds to an eNB of the existing LTEsystem. The NR gNB is connected to the NR UE 1 c-15 via a radio channeland may provide a service superior to the existing node B. In the nextgeneration mobile communication system, since all user traffics areserved through a shared channel, an apparatus for collecting stateinformation such as a buffer state, an available transmission powerstate, and a channel state of the UEs to perform scheduling is required.The NR NB 1 c-10 may serve as the device. One NR gNB generally controlsa plurality of cells. In order to realize high-speed data transmissioncompared with the current LTE, the NR gNB may have an existing maximumbandwidth, and may be additionally incorporated into a beam-formingtechnology and may be applied by using OFDM as a radio accesstechnology. Further, an AMC scheme determining a modulation scheme and achannel coding rate depending on a channel status of the terminal isapplied. The NR CN 1 c-05 may perform functions such as mobilitysupport, bearer setup, quality of service (QoS) setup, and the like. TheNR CN 1 c-05 is a device for performing a mobility management functionfor the terminal and various control functions and is connected to aplurality of base stations. In addition, the next generation mobilecommunication system can interwork with the existing LTE system, and theNR CN 1 c-05 is connected to the MME 1 c-25 through the networkinterface. The MME is connected to the eNB 1 c-30 which is the existingbase station.

FIG. 1D is a diagram of a radio protocol structure of a next generationmobile communication system, according to an embodiment of the presentdisclosure.

Referring to FIG. 1D, the radio protocol of the next generation mobilecommunication system is configured to include NR PDCPs 1 d-05 and 1d-40, NR RLCs 1 d-10 and 1 d-35, and NR MACs 1 d-15 and 1 d-30 in theterminal and the NR base station. The main functions of the NR PDCPs 1d-05 and 1 d-40 may include some of the following functions.

Header compression and decompression function (Header compression anddecompression: ROHC only)

Transfer of user data

In-sequence delivery function (In-sequence delivery of upper layer PDUs)

Reordering function (PDCP PDU reordering for reception)

Duplicate detection function (Duplicate detection of lower layer SDUs)

Retransmission function (Retransmission of PDCP SDUs)

Ciphering and deciphering function (Ciphering and deciphering)

Timer-based SDU discard function (Timer-based SDU discard in uplink)

The reordering function of the NR PDCP apparatus is for rearranging PDCPPDUs received in a lower layer in order based on a PDCP SN and mayinclude a function of transferring data to a higher layer in therearranged order, a function of recording PDCP PDUs lost by thereordering, a function of reporting a state of the lost PDCP PDUs to atransmitting side, and a function of requesting a retransmission of thelost PDCP PDUs.

The main functions of the NR RLCs 1 d-10 and 1 d-35 may include some ofthe following functions.

Data transfer function (Transfer of upper layer PDUs)

In-sequence delivery function (In-sequence delivery of upper layer PDUs)

Out-of-sequence delivery function (Out-of-sequence delivery of upperlayer PDUs)

ARQ function (Error correction through HARQ)

Concatenation, segmentation, reassembly function (Concatenation,segmentation and reassembly of RLC SDUs)

Re-segmentation function (Re-segmentation of RLC data PDUs)

Reordering function (Reordering of RLC data PDUs)

Duplicate detection function (Duplicate detection)

Error detection function (Protocol error detection)

RLC SDU discard function (RLC SDU discard)

RLC re-establishment function (RLC re-establishment)

The in-sequence delivery function of the NR RLC apparatus is fordelivering RLC SDUs received from a lower layer to a higher layer inorder, and may include a function of reassembling and transferring anoriginal one RLC SDU which is divided into a plurality of RLC SDUs andreceived, a function of rearranging the received RLC PDUs based on theRLC SN or the PDCP SN, a function of recording the RLC PDUs lost by thereordering, a function of reporting a state of the lost RLC PDUs to thetransmitting side, a function of requesting a retransmission of the lostRLC PDUs, a function of transferring only the SLC SDUs before the lostRLC SDU to the higher layer in order when there is the lost RLC SDU, afunction of transferring all the received RLC SDUs to the higher layerbefore a predetermined timer starts if the timer expires even if thereis the lost RLC SDU, or a function of transferring all the RLC SDUsreceived to the higher layer in order if the predetermined timer expireseven if there is the lost RLC SDU.

The out-of-sequence delivery function of the NR RLC apparatus is fordirectly delivering the RLC SDUs received from the lower layer to thehigher layer regardless of order, and may include a function ofreassembling and transferring an original RLC SDU which is divided intoseveral RLC SDUs and received, and a function of storing the RLC SN orthe PDCP SP of the received RLC PDUs and arranging it in order to recordthe lost RLC PDUs.

The NR MACs 1 d-15 and 1 d-30 may be connected to several NR RLC layerapparatuses configured in one terminal, and the main functions of the NRMAC may include some of the following functions.

Mapping function (Mapping between logical channels and transportchannels)

Multiplexing and demultiplexing function (Multiplexing/demultiplexing ofMAC SDUs)

Scheduling information reporting function (Scheduling informationreporting)

HARQ function (Error correction through HARQ)

Priority handling function between logical channels (Priority handlingbetween logical channels of one UE)

Priority handling function between terminals (Priority handling betweenUEs by dynamic scheduling)

MBMS service identification function (MBMS service identification)

Transport format selection function (Transport format selection)

Padding function (Padding)

The NR PHY layers 1 d-20 and 1 d-25 may perform channel-coding andmodulating higher layer data, making the higher layer data as an OFDMsymbol and transmitting them to a radio channel, or demodulating andchannel-decoding the OFDM symbol received through the radio channel andtransmitting the demodulated and channel-decoded OFDM symbol to thehigher layer.

FIG. 1E is a diagram of setting, by a terminal, each layer apparatus(entity, hereinafter, apparatus) in the next generation mobilecommunication, according to an embodiment of the present disclosure.

FIG. 1E also describes a procedure of setting a connection with anetwork via which a terminal transmits/receives data and settingapparatuses (entity, hereinafter, apparatuses) of each layer.

If there is data to be transmitted, a terminal 1 e-01 (hereinafter,referred to as an idle mode UE) for which no connection is currentlyestablished performs an RRC connection establishment procedure with theLTE base station or the NR base station 1 e-02. The terminal 1 e-01establishes uplink transmission synchronization with the base station 1e-02 through a random access procedure and transmits anRRCConnectionRequest message to the base station 1 e-02 (at step 1e-05). The message includes establishmentCause for connection with anidentifier of the terminal 1 e-01. The base station 1 e-02 transmits anRRCConnectionSetup message to allow the terminal 1 e-01 to set the RRCconnection (at step 1 e-10). The message may store RRC connectionconfiguration information, setting information of each layer, and thelike. In other words, it may include configuration information on thePHY or NR PHY apparatus, the MAC or NR MAC apparatus, the RLC or NR RLCapparatus, the PDCP or the NR PDCP apparatus, and the informationinstructing the setting for the specific functions among the functionsdescribed in FIG. 1B or 1D supported by the layer apparatuses. Inaddition, the message may include an indication of whether to allocate aPDCP SN in the PDCP apparatus or may include an indication of whether toallocate an RLC SN in the RLC apparatus. The RRC connection is alsocalled a signaling radio bearer (SRB) and is used for transmission andreception of the RRC message that is a control message between theterminal 1 e-01 and the base station 1 e-02. The terminal establishingthe RRC connection transmits an RRCConnetionSetupComplete message to thebase station (at step 1 e-15). The base station transmits anRRCConnectionReconfiguration message to the terminal in order to set upa data radio bearer (DRB) (at step 1 e-20). The configurationinformation of each layer and the like may be stored in the message. Inother words, it may include configuration information on the PHY or NRPHY apparatus, the MAC or NR MAC apparatus, the RLC or NR RLC apparatus,the PDCP or the NR PDCP apparatus, and the information instructing thesetting for the specific functions among the functions described in FIG.1B or 1D supported by the layer apparatuses. In addition, the messagemay include an indication of whether to allocate a PDCP SN in the PDCPapparatus or may include an indication of whether to allocate an RLC SNin the RLC apparatus. In addition, the message includes theconfiguration information of the DRB in which user data are processed,and the terminal applies the information to set the DRB and set thefunctions of each layer and transmits anRRCConnectionReconfigurationComplete message to the base station 1 e-02(at step 1 e-25). If the above procedure is completed, the terminal 1e-01 transmits and receives data to and from the base station 1 e-02 (atstep 1 e-30). While transmitting and receiving data, the base station 1e-02 may again transmit the RRCConnectionReconfiguration message to theterminal 1 e-01 (at step 1 e-35), if necessary, set the configurationinformation of each layer of the terminal 1 e-01. In other words, it mayinclude configuration information on the PHY or NR PHY apparatus, theMAC or NR MAC apparatus, the RLC or NR RLC apparatus, the PDCP or the NRPDCP apparatus, and the information instructing the setting for thespecific functions among the functions described in FIG. 1B or 1Dsupported by the layer apparatuses. In addition, the message may includean indication of whether to allocate a PDCP SN in the PDCP apparatus ormay include an indication of whether to allocate an RLC SN in the RLCapparatus. In addition, the message may include the information forsetting the interworking between the LTE base station (or NR basestation) and the NR base station. The information for setting theinterworking between the LTE base station and the NR base station mayinclude information indicating a 3C type or a 1A type, information oneach layer apparatus according to each type, and the like. Uponcompletion of the setting of apparatuses of each layer according to themessage, the terminal 1 e-01 transmits anRRCConnectionReconfigurationComplete message to the base station 1 e-02(at step 1 e-40).

FIGS. 1FA and 1FB are diagrams of a terminal that receives servicesthrough an LTE base station and an NR base station in the nextgeneration mobile communication system, according to an embodiment ofthe present disclosure.

In FIGS. 1FA and 1FB, 1 f-01 shows that the LTE base station is a master(MeNB) in the 3C type LTE base station-LTE base station interworking, 1f-02 shows that the LTE base station is a master (MeNB) in the 3C typeLTE base station-NR base station interworking, 1 f-03 shows that the NRbase station is a master (MeNB) in the 3C type LTE base station-NR basestation interworking, and 1 f-04 shows that the NR base station is amaster (MeNB) in the 3C type NR base station-NR base stationinterworking, 1 f-05 shows a 1A type LTE base station-NR base stationinterworking, 1 f-06 shows a 1A type NR base station-NR base stationinterworking, and 1F-07 shows the NR base station.

The LTE system allocates a PDCP SN in the PDCP apparatus, and allocatesan RLC SN in the RLC apparatus. However, in the next generation mobilecommunication systems, a PDCP SN may be allocated only in the NR PDCPdevice, and an RLC SN may not be allocated and a PDCP SN may be used inthe NR RLC apparatus. Therefore, the overhead may be reduced by deletingthe RLC SN. When a terminal accesses only one cell or a base station,the terminal can operate with a single SN without any problem. However,a problem may arise in the multiple access scenario described above withreference to FIGS. 1FA and 1FB. The above-mentioned problems that mayoccur are described with respect to FIGS. 1GA and 1GB.

FIGS. 1GA and 1GB are diagrams when one SN is used in the multipleaccess environment, according to an embodiment of the presentdisclosure.

In FIGS. 1GA and 1GB, 1 g-05 shows that the LTE base station is themaster (MeNB) in the 3C type interworking between the LTE base stationand the LTE base station and allocates the PDCP SN in the PDCP apparatusof the MeNB, and the RLC apparatuses of the MeNB and the RLC apparatusesof SeNB each allocate independent RLC SNs. Therefore, each RLC apparatuscan normally perform an RLC ARQ operation based on the RLC SN togetherwith the RLC apparatus of the receiving end.

In FIGS. 1GA and 1GB, 1 g-10 shows that the LTE base station is themaster (MeNB) in the 3C type interworking between the LTE base stationand the NR base station, the PDCP SN is assigned in the MeNB PDCPapparatus of the MeNB, and since the RLC apparatus of the MeNB allocatesthe independent RLC SN and the NR RLC apparatus of the SeNB supports oneSN, the RLC apparatus may reuse the PDCP SN without changing it. The RLCapparatus of the MeNB can normally perform an RLC ARQ operation based onthe RLC SN together with the RLC apparatus of the receiving end.However, the NR RLC apparatus of the SeNB cannot normally perform theRLC ARQ operation together with the NR RLC apparatus of the receivingend. For example, if it is assumed that the NR RLC apparatus of thetransmitting end transmits SNs 1, 2, and 4 to the receiving end and thatthe receiving end normally receives the SNs, the receiving end cannotknow whether the SN 3 is lost during the transmission or whether the SN3 is originally transmitted from another MeNB. Therefore, the NR RLCapparatus of the receiving end continuously waits for the SN 3. As aresult, the transmission delay may occur and the window stalling problemmay occur. Such a problem may occur in the NR RLC apparatus of thetransmitting end in the scenarios 1 f-02, 1 f-03, and 1 f-04 in FIGS.1FA and 1FB.

FIG. 1H is a diagram in which multiple access is supported by one SN,according to an embodiment of the present disclosure in the presentdisclosure.

In FIG. 1H, 1 h-01 shows that the LTE base station is the master (MeNB)in the 3C type LTE base station-NR base station interworking, the PDCPSN is allocated in the MeNB PDCP apparatus of the MeNB, and since theRLC apparatus of the MeNB allocates the independent RLC SN and the NRRLC apparatus of the SeNB supports one SN, the RLC apparatus may reusethe PDCP SN without changing it. Therefore the transmission delay andwindow stalling problem that is mentioned in FIGS. 1GA and 1GB mayoccur. In 1 f-02, 1 f-03, and 1 f-04 in FIGS. 1FA and 1FB in which thesame problem as described above, a method for inserting into an RLCheader a SN that the NR RLC apparatus transmits as in 1 h-05 may beused. That is, since the SN is the first RLC PDU of the corresponding NRRLC layer, the SN 1 indicating itself can be inserted into the RLCheader (if the same SN is inserted, it may indicate the first RLC PDU).SN 2 that is transmitted subsequently may insert the SN 1 because it wasthe previous SN. SN 4 that is transmitted subsequently may insert the SN2 because it was the previous SN. Therefore, if the NR RLC apparatus ofthe transmitting end transmits the SNs 1, 2, and 4 and the NR RLCapparatus successfully receives them, it can be confirmed that theprevious SN is 2 in the header of the RLC PDU of the SN 4 and the SN 3is transmitted in another MeNB. Therefore, the NR RLC apparatus of thetransmitting end and the receiving end can normally perform the RLC ARQoperation. This operation can be equally applied to the NR RLC apparatusof the scenarios such as 1 f-02, 1 f-03, and 1 f-04 in FIGS. 1FA and1FB.

FIG. 1I is a diagram in which multiple access is supported by one SN,according to an embodiment of the present disclosure.

In FIG. 1I, 1 i-01 shows that the LTE base station is the master (MeNB)in the 3C type interworking between the LTE base station and the NR basestation, the PDCP SN is assigned in the MeNB PDCP apparatus of the MeNB,and since the RLC apparatus of the MeNB allocates the independent RLC SNand the NR RLC apparatus of the SeNB supports one SN, the RLC apparatusmay reuse the PDCP SN without changing it. Therefore the transmissiondelay and window stalling problem that is mentioned in FIGS. 1GA and 1GBmay occur. In the scenarios such as 1 f-02, 1 f-03, and 1 f-04 in FIGS.1FA and 1FB in which the same problem as described above may occur, amethod for inserting into an RLC header a gap between the SN the NR RLCapparatus transmits just before 1 i-05 and the currently transmitted SNcan be used. Here, if the gap is 0, it indicates the first RLC PDU inthe corresponding connection. That is, since the SN 1 is the first RLCPDU of the corresponding NR RLC layer, the gap 0 can be inserted intothe RLC header. SN 2 that is transmitted subsequently may insert gap 1because a gap (2−1=1) from the just previous SN is 1. SN 4 that istransmitted subsequently may insert the gap 2 which is a gap (4−2=2)from the just previous SN, because the just previous SN is 2. Therefore,if the NR RLC apparatus of the transmitting end transmits the SNs 1, 2,and 4 and the NR RLC apparatus successfully receives them, it can beconfirmed that the gap from the previous SN is 2 in the header of theRLC PDU of the SN 4 and the SN 3 is transmitted in another MeNB.Therefore, the NR RLC apparatus of the transmitting end and thereceiving end can normally perform the RLC ARQ operation. The aboveoperations can be equally applied to the NR RLC apparatus of thescenarios such as 1 f-02, 1 f-03, and 1 f-04 in FIGS. 1FA and 1FB.Instead of the method for inserting into the RLC header the gap betweenthe SN that the NR RLC apparatus transmits just before and the currentlytransmitted SN t, a method for inserting into an MAC subheader a gapbetween a SN (or other indicators) that the NR MAC apparatus transmitsjust before and the currently transmitted SN (or other indicators) maybe applied. In this case, other indicators may be an indicatorindicating the order of the corresponding packet.

FIG. 1J is a diagram in which multiple access is supported by one SN,according to an embodiment of the present disclosure.

In FIG. 1J, 1 j-01 shows that the LTE base station is the master (MeNB)in the 3C type interworking between the LTE base station and the NR basestation, the PDCP SN is assigned in the MeNB PDCP apparatus of the MeNB,and since the RLC apparatus of the MeNB allocates the independent RLC SNand the NR RLC apparatus of the SeNB supports one SN, the RLC apparatusmay reuse the PDCP SN without changing it. Therefore the transmissiondelay and window stalling problem that is mentioned in FIGS. 1GA and 1GBmay occur. In the scenarios such as 1 f-02, 1 f-03, and 1 f-04 in FIGS.1FA and 1FB in which the same problem as described above may occur, amethod for inserting into an RLC header a gap between the SN the NR RLCapparatus transmits just before like 1 j-05 and the currentlytransmitted SN can be used. The method for coding and inserting a gapbetween SNs in the NR RLC apparatus is the same as that of FIG. 1I, andif a gap is 0, it indicates the first RLC PDU in the correspondingconnection.

However, if the gap is encoded and put in the header of all RLC PDUs,the overhead may be increased. For example, if it is assumed that thePDCP SN has a length of 18 bits, the length of the gap needs to have 18bits (since the PDCP SN is separated and transmitted as MeNB and SeNB,the gap may need to indicate the whole space of the PDCP sequence).Therefore, since an 18-bit gap is inserted in the RLC header of all RLCPDUs, the overhead can be increased. To reduce the overhead, a gapindicator (GI) field having a size of 1 bit in the RLC header is definedas in Table 1-1.

TABLE 1-1 GI field Description 0  5 bits gap field 1 12 bits gap field

The GI field value and information can be mapped to two different cases.

That is, if the GI field having a size of 1 bit is defined in the RLCheader and thus the GI field value is 0, it may indicate that the gap isnot inserted into the RLC header, and if the GI field value is 1, it mayindicate that the gap is inserted into the RLC header. The case in whichit is not necessary to insert the gap into the RLC header in the 1-2-2embodiment corresponds to the case in which the RLC PDUs have aconsecutive SN or do not correspond to a first segment among segments ofone RLC PDU. For example, in the case of the SN 1 such as 1 j-10, sinceit is the first RLC PDU of the corresponding connection, to indicatethis, the GI field may be set to be 1 to indicate that there is a gapand insert a gap value as 0. In the case of the SN 2, there is no needto insert an interval value because it is a SN that is consecutive withthe previous SN 1. Therefore, the GI field is set to be 0 and theoverhead is reduced without inserting a gap value into the RLC header.In the case of the SN 4, there is no need to insert a gap value becauseit is not a SN that is consecutive with the previous SN 2. Therefore,the GI field is set to be 1 and the gap value 2 is inserted into the RLCheader. In the case of the segments of one RLC PDU, in the case of thefirst segment, the gap value with the previous SN is inserted into theRLC header and the segment may not be inserted in other cases. If thefirst segment has the SN consecutive to the previous SN, the GI field isset to be 0 and thus the gap value may also be omitted.

Therefore, if the NR RLC apparatus of the transmitting end transmits theSNs 1, 2, and 4 and the NR RLC apparatus successfully receives them,since the GI field is set to be 1 in the RLC PDU of the SN 4, it can beconfirmed that there is the gap value, and it can be confirmed that thegap from the previous SN is 2 and the SN 3 is transmitted from anotherMeNB. Therefore, the NR RLC apparatus of the transmitting end and thereceiving end can normally perform the RLC ARQ operation. Theseoperations can be equally applied to the NR RLC apparatus of thescenarios such as 1 f-02, 1 f-03, and 1 f-04 in FIGS. 1FA and 1FB.Instead of the method for inserting into the RLC header the gap betweenthe SN that the NR RLC apparatus transmits just before and the currentlytransmitted SN, a method for inserting into an MAC subheader a gapbetween a SN (or other indicators) that the NR MAC apparatus transmitsjust before and the currently transmitted SN (or other indicators) maybe applied. In this case, other indicators may be an indicatorindicating the order of the corresponding packet. In addition, the GIfield is defined in the MAC subheader field and may be identical to andmodified as described above to be applied to the MAC subheader.

FIG. 1K is a diagram in which multiple access is supported by one SN,according to an embodiment of the present disclosure.

In FIG. 1K, 1 k-01 shows that the LTE base station is the master (MeNB)in the 3C type LTE base station-NR base station interworking, the PDCPSN is allocated in the MeNB PDCP apparatus of the MeNB, and since theRLC apparatus of the MeNB allocates the independent RLC SN and the NRRLC apparatus of the SeNB supports one SN, the RLC apparatus may reusethe PDCP SN without changing it. Therefore the transmission delay andwindow stalling problem that is mentioned in FIGS. 1GA and 1GB mayoccur. In the scenarios such as 1 f-02, 1 f-03, and 1 f-04 in FIGS. 1FAand 1FB in which the same problem as described above may occur, a methodfor inserting into an RLC header a gap between the SN the NR RLCapparatus transmits just before 1 k-05 and the currently transmitted SNcan be used. The method for encoding and inserting a gap between the SNsin the NR RLC apparatus is the same as that of FIG. 1I.

However, if the gap is encoded and put in the header of all RLC PDUs,the overhead may be increased. For example, if it is assumed that thePDCP SN has a length of 18 bits, the length of the gap needs to have 18bits (since the PDCP SN is separated and transmitted as MeNB and SeNB,the gap may need to indicate the whole space of the PDCP sequence).Therefore, in this case, since an 18-bit gap is inserted in the RLCheader of all RLC PDUs, the overhead can be increased. To reduce theoverhead, a GI field having a size of 2 bits defined in the RLC headeris defined in Table 1-2.

TABLE 1-2 GI field Description 00 The first RLC PDU without gap 01 Nogap for continuous RLC PDU 10 Gap 11 No gap for segments

The GI field value and information can be mapped to 24 different cases,and the present disclosure includes the same.

That is, if the GI field having a size of 2 bits is defined in the RLCheader and thus the GI field value is 00, it may be indicated that thefirst RLC PDU is in the corresponding connection and the gap is notinserted into the RLC header, if the GI field value is 01, it may beindicated that the current SN is a sequence consecutive to the previoussequence and thus the gap need not to be inserted into the RLC header,if the GI field value is 10, it may be indicated that the gap betweenthe previous SN and the current SN is present and thus the gap isinserted into the RLC header, and if the GI field value 11, it may beindicated that it is segments of one RLC PDU and thus the gap is notinserted. In the case of the first segment among the segments, there isa need to insert the gap. However, if the SN of the first segment isconsecutive with the previous SN, the gap may be omitted. The case inwhich it is not necessary to insert the gap into the RLC headercorresponds to the case in which the RLC PDUs have a consecutive SN ordo not correspond to a first segment among segments of one RLC PDU. Forexample, in the case of SN 1 such as 1 k-10, since it is the first RLCPDU, the GI field is set to be 00 to indicate it and the gap may beomitted to reduce the overhead. In the case of the SN 2, there is noneed to insert an interval value because it is a SN that is consecutivewith the previous SN 1. Therefore, the GI field is set to be 01 and theoverhead is reduced without inserting a gap value into the RLC header.In the case of the SN 4, there is no need to insert a gap value becauseit is not a SN that is consecutive with the previous SN 2. Therefore,the GI field is set to be 10 and the gap value 2 is inserted into theRLC header. In the case of the segments of one RLC PDU, in the case ofthe first segment, the gap value with the previous SN is inserted intothe RLC header and the segment may not be inserted in other cases. Ifthe first segment has the SN consecutive to the previous SN, the GIfield is set to be 0 and thus the gap value may also be omitted.

Therefore, if the NR RLC apparatus of the transmitting end transmits theSNs 1, 2, and 4 and the NR RLC apparatus successfully receives them,since the GI field is set to be 10 in the RLC PDU of the SN 4, it can beconfirmed that there is the gap value, and it can be confirmed that thegap from the previous SN is 2 and the SN 3 is transmitted from anotherMeNB. Therefore, the NR RLC apparatus of the transmitting end and thereceiving end can normally perform the RLC ARQ operation. Theseoperations can be equally applied to the NR RLC apparatus of thescenarios such as 1 f-02, 1 f-03, and 1 f-04 in FIGS. 1FA and 1FB.Instead of the method for inserting into the RLC header the gap betweenthe SN that the NR RLC apparatus transmits just before and the currentlytransmitted SN, a method for inserting into an MAC subheader a gapbetween a SN (or other indicators) that the NR MAC apparatus transmitsjust before and the currently transmitted SN (or other indicators) maybe applied. In this case, other indicators may be an indicatorindicating the order of the corresponding packet. In addition, the GIfield is defined in the MAC subheader field and may be identical to andmodified as described above to be applied to the MAC subheader.

FIG. 1L is a diagram in which multiple access is supported by one SN,according to an embodiment of the present disclosure.

In FIG. 1L, 1 l-01 shows that the LTE base station is the master (MeNB)in the 3C type LTE base station-NR base station interworking, the PDCPSN is allocated in the MeNB PDCP apparatus of the MeNB, and since theRLC apparatus of the MeNB allocates the independent RLC SN and the NRRLC apparatus of the SeNB supports one SN, the RLC apparatus may reusethe PDCP SN without changing it. Therefore the transmission delay andwindow stalling problem that is mentioned in FIGS. 1GA and 1GB mayoccur. In the scenarios such as 1 f-02, 1 f-03, and 1 f-04 in FIGS. 1Faand 1FB in which the same problem as described above may occur, a methodfor inserting into an RLC header a gap between the SN the NR RLCapparatus transmits just before 1 l-05 and the currently transmitted SNcan be used. The method for coding and inserting a gap between SNs inthe NR RLC apparatus is the same as that of FIG. 1I, and if a gap is 0,it indicates the first RLC PDU in the corresponding connection. Inaddition, a gap is encoded and put in all the RLC PDUs; however, toreduce the overhead, a variable gap size is used.

For example, if it is assumed that the PDCP SN has a length of 12 bits,the length of the gap needs to have 12 bits (since the PDCP SN isseparated and transmitted as MeNB and SeNB, the gap may need to indicatethe whole space of the PDCP sequence. Therefore, in this case, since a12-bit gap is inserted in the RLC header of all RLC PDUs, the overheadcan be increased. A gap length (GL) field having a size of 1 bit isdefined in the RLC header to reduce the overhead. In the abovedescription, a predetermined bit may have several bits, and if x bitsare included, a size of 2{circumflex over ( )}x gap fields may beindicated. For example, a 1-bit GL field may be defined as in Table 1-3.

TABLE 1-3 GI field Description 0  5 bits gap field 1 12 bits gap field

The mapping information may indicate a size of various gap fields usingseveral bits.

That is, if the GL field having a size of 1 bit is defined in the RLCheader and thus the field value is 0, a field having a length of 5 bitsis used to indicate a gap in the corresponding RLC PDU, and if the GLfield value is 1, a field having a length of 12 bits is used to indicatethe gap in the PDU. For example, in the case of the SN 1 such as 11-10,since it is the first RLC PDU of the corresponding connection, the GIfield is set to be 00 to indicate it and the gap having a size of 5 bitsmay be used to reduce the overhead. In the case of the SN 2, since it isa SN consecutive to the previous SN 1, the gap value is reduced, so theGL field is set to be 0 and the gap having a size of 5 bits may be used.Even in the case of the SN 4, since it the previous SN 2 and the gapvalue are reduced, so the GL field is set to be 0 and the gap having asize of 5 bits may be used. However, in the case of the SN 1010, sincethe gap from the previous SN 4 is large, it is possible to set a GLfield to be 1 and use a gap having a size of 12 bits.

Therefore, if the NR RLC apparatus of the transmitting end transmits theSNs 1, 2, and 4 and the NR RLC apparatus successfully receives them,since the GI field is set to be 0 in the RLC PDU of the SN 4, it can beconfirmed that there is the gap value having a size of 5 bits, and itcan be confirmed that the gap from the previous SN is 2 and the SN 3 istransmitted from another MeNB. Therefore, the NR RLC apparatus of thetransmitting end and the receiving end can normally perform the RLC ARQoperation. These operations can be equally applied to the NR RLCapparatus of the scenarios such as 1 f-02, 1 f-03, and 1 f-04 in FIGS.1FA and 1FB. Instead of the method for inserting into the RLC header thegap between the SN that the NR RLC apparatus transmits just before andthe currently transmitted SN, a method for inserting into an MACsubheader a gap between a SN (or other indicators) that the NR MACapparatus transmits just before and the currently transmitted SN (orother indicators) may be applied. In this case, other indicators may bean indicator indicating the order of the corresponding packet. Inaddition, the GI field is defined in the MAC subheader field and may beidentical to and modified as described above to be applied to the MACsubheader.

In the next generation mobile communication systems, a high data rate issupported, so if data is missed, a large amount of data is likely to belost. Therefore, an RLC status report method is needed. The presentdisclosure proposes various RLC status reporting methods suitable forthe next generation mobile communication system. The RLC statusreporting methods proposed below can identically be transmitted in asingle access environment connecting only to the LTE or the NR as wellas the multiple access environment as described above.

FIG. 1M is a diagram of a RLC status reporting method, according to anembodiment of the present disclosure.

FIG. 1M an RLC status report can be sent from a receiving side RLC layerapparatus to a transmitting side RLC layer apparatus (assuming a 10 bitRLC SN length).

The receiving side RLC layer apparatus stores the received RLC PDUs inthe receiving buffer and then checks the SN to recognize the SN of theRLC PDU missed during the transmission. If the predetermined conditionis satisfied, the receiving side RLC layer apparatus generates an RLCstatus report message and transmits the generated RLC status reportmessage to the transmitting side RLC layer apparatus. The RLC statusreport message includes information on the RLC PDU reception state ofthe receiving side RLC layer apparatus, and the transmitting side RLClayer apparatus identifies that the RLC PDU successfully transmitted andthe RLC PDU failed to transmit, through the RLC status report message.The RLC status report message may be 1 m-05 in FIG. 1M. The RLC statusreport message includes one ACK_SN or one ACK_SN and one or more NACK.The presence of NACK_SN is indicated by an E1 field. The E1 fieldindicates one NACK_SN, an E1 field, and an E2 field follow, and the E2field indicates whether or not SOstart and SOend fields indicating apart of the NACK_SN follow. The ACK_SN field includes the next SN of thehighest SN among the SNs of RLC PDUs successfully received so far andthe NACK_SN includes the SNs of the RLC PDUs that have not beenreceived. For example, the transmitting side RLC layer apparatustransmits RLC PDU 7 to RLC PDU 10 at any time, and the receiving sideRLC layer apparatus receives only RLC PDU 7 and RLC PDU 9 and stores thereceived RLC PDU 7 and RLC PDU 9 in the receiving buffer. If the RLCstatus report message generation condition is satisfied at any time, thereceiving side RLC layer apparatus generates the RLC status reportmessage. A SN 10 is included in the ACK_SN field of the RLC statusreport message, and a SN 8 is included in the NACK_SN field. Thetransmitting side RLC layer apparatus receiving the RLC status reportmessage determines that the RLC PDU having a SN lower than the lowestNACK_SN, that is, the RLC PDUs having a SN lower than 7 is successfullytransmitted and discards it in a retransmission buffer. In addition,PDCP SDUs mapped to the RLC PDUs having a SN lower than 7 among the PDCPSDUs stored in the transmission buffer is also discarded. Thetransmitting side RLC layer apparatus retransmits the RLC PDU 8reporting that the receiving side RLC layer apparatus has not received.

The RLC layer apparatus transmits the RLC PDU with the SN, and checkswhether the transmitted RLC PDU succeeds based on the RLC status reportmessage and retransmits the RLC PDU, thereby ensuring reliabletransmission/reception.

By receiving a general RLC status report message, the transmitting sideRLC layer apparatus acquires the following two pieces of informationlargely.

Identify RLC PDU failed in transmission

Identify RLC PDU succeeded in transmission

It is recognized which RLC PDU to retransmit in the future byidentifying the RLC PDU failing to transmit, and it determines which RLCPDU or PDCP SDU of RLC PDUs or PDCP SDUs stored in the retransmissionbuffer and the transmission buffer is discarded.

The fields applied to the RLC status reporting method for the presentdisclosure are as follows.

The D/C field has a length of 1 bit and indicates whether the RLC PDU isan RLC data PDU or an RLC control PDU as in Table 1-4.

TABLE 1-4 D/C field value Description 0 Control PDU 1 Data PDU

The CPT field has a length of 1 bit and indicates a kind of RLC controlPDU, as in Table 1-5.

TABLE 1-5 CPT field value Description 000 STATUS PDU 001-111 Reserved(PDUs with this coding will be discarded by the receiving entity forthis release of the protocol)

ACK_SN indicates the next SN of the RLC PDU that has not yet beenreceived and a SN that is not reported as missed in the RLC statusreport. Upon receiving the RLC status report at the transmitting end, itis determined that the SN indicated by the ACK_SN is not included, theSN indicated by the NACK_SN is not included, and a SN smaller thanACK_SN has been received successfully (when the NACK_SN is indicatedtogether with the SOstart and the SOend, it is determined that theSOstart and the SOend successfully receive only a part other than thepart indicated by the NACK_SN). The ACK_SN has a predetermined length,and the predetermined length can be variously defined such as 10 bits,16 bits, or 18 bits.

The E1 field has a length of 1 bit and indicates whether or not theNACK_SN, the E1 field, and the E2 field follow as in Table 1-6.

TABLE 1-6 E1 field value Description 0 A set of NACK_SN, E1 and E2 doesnot follow. 1 A set of NACK_SN, E1 and E2 follows.

NACK_SN indicates the SN of the missed RLC PDU, and may indicate a partof the lost RLC PDU together with SOstart and SOend. The NACK_SN has apredetermined length, and the predetermined length can be variouslydefined such as 10 bits, 16 bits, or 18 bits.

The E2 field has a length of 1 bit and indicates whether the SOstart andthe SOend follow as in Table 1-7.

TABLE 1-7 E2 field value Description 0 A set of SOstart and SOend doesnot follow for this NACK_SN. 1 A set of SOstart and SOend follows forthis NACK_SN.

The SOstart field indicates a head position of the part when indicatinga part of the NACK_SN. The head position may be indicated by a byteunit. The SOstart has a predetermined length, and the predeterminedlength can be variously defined such as 15 bits, 16 bits, and 18 bits.

The SOend field indicates a tail position of the part when indicating apart of the NACK_SN. The tail position may be indicated by a byte unit.The SOend has a predetermined length, and the predetermined length canbe variously defined such as 15 bits, 16 bits, and 18 bits.

The RLC status reporting method proposed above can be equally applied tothe NR RLC apparatus of 1 f-02, 1 f-03, and 1 f-04 in FIGS. 1FA and 1FB.

FIG. 1N shows an RLC status reporting method, according to an embodimentof the present disclosure.

In FIG. 1N an RLC status report can be sent from a receiving side RLClayer apparatus to a transmitting side RLC layer device according to aRLC status reporting method (assuming a 10 bit RLC SN length).

The receiving side RLC layer device stores the received RLC PDUs in thereceiving buffer and then checks the SN to recognize the SN of the RLCPDU missed during the transmission. If the predetermined condition issatisfied, the receiving side RLC layer apparatus generates an RLCstatus report message and transmits the generated RLC status reportmessage to the transmitting side RLC layer apparatus. The RLC statusreport message includes information on the RLC PDU reception state ofthe receiving side RLC layer apparatus, and the transmitting side RLClayer apparatus identifies the RLC PDU successfully transmitted and theRLC PDU failed to transmit, through the RLC status report message. TheRLC status report message may be written as 1 n-05 in FIG. 1N. The RLCstatus report message includes one ACK_SN or a set of one ACK_SN and oneor more LOWER_SN, UPPER_SN, E1, and E2 fields. It is indicated by the E1field whether there are the set of LOWER_SN, UPPER_SN, E1, and E2fields. The E1 field indicates whether a set of one LOWER_SN field, theUPPER_SN field, the E1 field, and the E2 field follow, and the E2 fieldindicates whether or not SOstart and SOend fields indicating a part ofthe NACK_SN follow. The ACK_SN field includes the next SN of the highestSN among the SNs of RLC PDUs that have successfully been received andthe NACK_SN includes the lowest SN that has successfully been received.The UPPER_SN may include the highest SN that has not been received. TheLOWER_SN and the UPPER_SN may include the SN by various predeterminedmethods to indicate a range of a large number of missed SNs. That is,the RLC apparatus of the receiving end may request the retransmission tothe RLC apparatus of the transmitting end since the RLC PDUscorresponding to all SNs between the LOWER_SN<SN<=UPPER_SN is missed.For example, the transmitting side RLC layer apparatus transmits RLC PDU5 to RLC PDU 80 at any time, and the receiving side RLC layer apparatusreceives only RLC PDU 5, RLC PDU 78, RLC PDU 79, and RLC PDU 80 andstores the received RLC PDU 5, RLC PDU 78, RLC PDU 79, and RLC PDU 80 inthe receiving buffer. If the RLC status report message generationcondition is satisfied at any time, the receiving side RLC layerapparatus generates the RLC status report message. The ACK_SN field ofthe RLC status reporting message may include SN 81, the LOWER_SN fieldmy include SN 5, and the UPPER_SN may include 77. The transmitting sideRLC layer apparatus receiving the RLC status report message determinesthat the RLC PDU having a SN lower than the lowest LOWER_SN, that is,the RLC PDUs having a SN lower than 5 is successfully transmitted anddiscards it in a retransmitting buffer. In addition, PDCP SDUs mapped tothe RLC PDUs having a SN lower than 5 among the PDCP SDUs stored in thetransmission buffer is also discarded. The transmitting side RLC layerapparatus retransmits the RLC PDU 6 to RLC PDU 77 reporting that thereceiving side RLC layer apparatus has not received.

When the first RLC PDU of the RLC layer apparatus of the transmittingend is missed, the LOWER_SN may be allocated as the same value as theUPPER_SN to notify the transmitting end that all the SNs smaller thanthe UPPER_SN are not received. For example, if the LOWER_SN fieldincludes a SN 77 and the UPPER_SN includes 77, (SN<=77) may beindicated. When the first RLC PDU is missed, the LOWER_SN and theUPPER_SN may be defined by various methods. Alternatively, another fieldmay be defined.

The RLC layer apparatus transmits the RLC PDU with the SN, and checkswhether the transmitted RLC PDU succeeds based on the RLC status reportmessage and retransmits the RLC PDU, thereby ensuring reliabletransmission/reception.

By receiving a general RLC status report message, the transmitting sideRLC layer apparatus acquires the following two pieces of informationlargely.

Identify RLC PDU failed in transmission

Identify RLC PDU succeeded in transmission

It is recognized which RLC PDU to retransmit in the future byidentifying the RLC PDU failing to transmit, and it determines which RLCPDU or PDCP SDU of RLC PDUs or PDCP SDUs stored in the retransmissionbuffer and the transmission buffer is discarded.

The fields applied to the RLC status reporting method for the presentdisclosure are as follows.

The D/C field has a length of 1 bit and indicates whether the RLC PDU isan RLC data PDU or an RLC control PDU as in Table 1-8.

TABLE 1-8 D/C field value Description 0 Control PDU 1 Data PDU

The CPT field has a length of 1 bit and indicates a kind of RLC controlPDU as in Table 1-9.

TABLE 1-9 CPT field value Description 000 STATUS PDU 001-111 Reserved(PDUs with this coding will be discarded by the receiving entity forthis release of the protocol)

ACK_SN indicates the next SN of the RLC PDU that has not yet beenreceived and a SN that is not reported as missed in the RLC statusreport. Upon receiving the RLC status report at the transmitting end, itis determined that the SN indicated by the ACK_SN is not included, theSNs indicated by the LOWER_SN and the UPPER_SN are not included, and aSN smaller than ACK_SN has been received successfully (when the UPPER_SNis indicated together with the SOstart and the SOend, it is determinedthat the SOstart and the SOend successfully receive only a part otherthan the part indicated by the UPPER_SN). The ACK_SN has a predeterminedlength, and the predetermined length can be variously defined such as 10bits, 16 bits, or 18 bits.

The E1 field has a length of 1 bit and indicates whether or not theLOWER_SN, the UPPER_SN, the E1 field, and the E2 field follow, as inTable 1-10.

TABLE 1-10 E1 field value Description 0 A set of LOWER_SN, UPPER_SN, E1and E2 does not follow. 1 A set of LOWER_SN, UPPER_SN, E1 and E2follows.

The LOWER_SN may include the lowest SN that has successfully beenreceived. The UPPER_SN may include the highest SN that has not beenreceived. The LOWER_SN and the UPPER_SN may include the SN by variouspredetermined methods to indicate a range of a large number of missedSNs. The LOWER_SN and UPPER_SN have a predetermined length, and thepredetermined length can be variously defined such as 10 bits, 16 bits,or 18 bits. When the first RLC PDU of the RLC layer apparatus of thetransmitting end is missed, the LOWER_SN may be allocated as the samevalue as the UPPER_SN to notify the transmitting end that all the SNssmaller than the UPPER_SN are not received. For example, if the LOWER_SNfield includes a SN 77 and the UPPER_SN includes 77, (SN<=77) may beindicated. When the first RLC PDU is missed, the LOWER_SN and theUPPER_SN may be defined by various methods. Alternatively, another fieldmay be defined.

The E2 field has a length of 1 bit and indicates whether the SOstart andthe SOend follow, as in Table 1-11.

TABLE 1-11 E2 field value Description 0 A set of SOstart and SOend doesnot follow for this UPPER_SN. 1 A set of SOstart and SOend follows forthis UPPER_SN.

The SOstart field indicates a head position of the part when indicatinga part of the UPPER_SN. The head position may be indicated by a byteunit. The SOstart has a predetermined length, and the predeterminedlength can be variously defined such as 15 bits, 16 bits, and 18 bits.

The SOend field indicates a tail position of the part when indicating apart of the UPPER_SN. The tail position may be indicated by a byte unit.The SOend has a predetermined length, and the predetermined length canbe variously defined such as 15 bits, 16 bits, and 18 bits.

The 1 RLC status reporting method proposed above can be equally appliedto the NR RLC apparatus of 1 f-02, 1 f-03, and 1 f-04 in FIGS. 1FA and1FB.

FIG. 1O is a diagram of an RLC status reporting method, according to anembodiment of the present disclosure.

In FIG. 1O an RLC status report is sent from a receiving side RLC layerapparatus to a transmitting side RLC layer device (assuming a 10 bit RLCSN length).

The receiving side RLC layer device stores the received RLC PDUs in thereceiving buffer and then checks the SN to recognize the SN of the RLCPDU missed during the transmission. If the predetermined condition issatisfied, the receiving side RLC layer apparatus generates an RLCstatus report message and transmits the generated RLC status reportmessage to the transmitting side RLC layer apparatus. The RLC statusreport message includes information on the RLC PDU reception state ofthe receiving side RLC layer apparatus, and the transmitting side RLClayer apparatus identifies the RLC PDU successfully transmitted and theRLC PDU failed to transmit, through the RLC status report message. TheRLC status report message may be written as 1 o-05 in FIG. 1O. The RLCstatus report message includes one ACK_SN or a set of one ACK_SN and oneor more LOWER_SN, E2, UPPER_SN, E1, and E2 fields. It is indicated bythe E1 field whether there are the set of LOWER_SN, UPPER_SN, E1, and E2fields. The E1 field indicates whether a set of one LOWER_SN field, theE2 UPPER_SN field, the E1 field, and the E2 field follow, and the E2field indicates whether or not SOstart and SOend fields indicating apart of the LOWER_SN or the UPPER_SN follow. The ACK_SN field includesthe next SN of the highest SN among the SNs of RLC PDUs that have beensuccessfully received and the NACK_SN includes the lowest SN that hasbeen successfully received. The UPPER_SN may include the highest SN thathas not received so far. The LOWER_SN and the UPPER_SN may include theSN by various predetermined methods to indicate a range of a largenumber of missed SNs. That is, as an example, the RLC apparatus of thereceiving end may request the retransmission to the RLC apparatus of thetransmitting end since the RLC PDUs corresponding to all SNs between theLOWER_SN<SN<=UPPER_SN is missed. For example, the transmitting side RLClayer apparatus transmits RLC PDU 5 to RLC PDU 80 at any time, and thereceiving side RLC layer apparatus receives only RLC PDU 5, RLC PDU 78,RLC PDU 79, and RLC PDU 80 and stores the received RLC PDU 5, RLC PDU78, RLC PDU 79, and RLC PDU 80 in the receiving buffer. If the RLCstatus report message generation condition is satisfied at any time, thereceiving side RLC layer apparatus generates the RLC status reportmessage. The ACK_SN field of the RLC status reporting message mayinclude SN 81, the LOWER_SN field my include SN 5, and the UPPER_SN mayinclude 77. The transmitting side RLC layer apparatus receiving the RLCstatus report message determines that the RLC PDU having a SN lower thanthe lowest LOWER_SN, that is, the RLC PDUs having a SN lower than 5 issuccessfully transmitted and discards it in a retransmitting buffer. Inaddition, PDCP SDUs mapped to the RLC PDUs having a SN lower than 5among the PDCP SDUs stored in the transmission buffer is also discarded.The transmitting side RLC layer apparatus retransmits the RLC PDU 6 toRLC PDU 77 reporting that the receiving side RLC layer apparatus has notreceived.

When the first RLC PDU of the RLC layer apparatus of the transmittingend is missed, the LOWER_SN may be allocated as the same value as theUPPER_SN to notify the transmitting end that all the SNs smaller thanthe UPPER_SN are not received. For example, if the LOWER_SN fieldincludes a SN 77 and the UPPER_SN includes 77, (SN<=77) may beindicated. When the first RLC PDU is missed, the LOWER_SN and theUPPER_SN may be defined by various methods. Alternatively, another fieldmay be defined.

The RLC layer apparatus transmits the RLC PDU with the SN, and checkswhether the transmitted RLC PDU succeeds based on the RLC status reportmessage and retransmits the RLC PDU, thereby ensuring reliabletransmission/reception.

By receiving a general RLC status report message, the transmitting sideRLC layer apparatus acquires the following two pieces of information.

Identify RLC PDU failed in transmission

Identify RLC PDU succeeded in transmission

It is recognized which RLC PDU to retransmit in the future byidentifying the RLC PDU failing to transmit, and it determines which RLCPDU or PDCP SDU of RLC PDUs or PDCP SDUs stored in the retransmissionbuffer and the transmission buffer is discarded.

The fields applied to the 1-3-3-th RLC status reporting method for thepresent disclosure are as follows.

The D/C field has a length of 1 bit and indicates whether the RLC PDU isan RLC data PDU or an RLC control PDU as in Table 1-12.

TABLE 1-12 D/C field value Description 0 Control PDU 1 Data PDU

The CPT field has a length of 1 bit and indicates a kind of RLC controlPDU as in Table 1-13.

TABLE 1-13 CPT field value Description 000 STATUS PDU 001-111 Reserved(PDUs with this coding will be discarded by the receiving entity forthis release of the protocol)

ACK_SN indicates the next SN of the RLC PDU that has not yet beenreceived and a SN that is not reported as missed in the RLC statusreport. Upon receiving the RLC status report at the transmitting end, itis determined that the SN indicated by the ACK_SN is not included, theSNs indicated by the LOWER_SN and the UPPER_SN are not included, and aSN smaller than ACK_SN has been received successfully (when the LOWER_SNis indicated together with the SOstart and the SOend or the UPPER_SN isindicated together with the SOstart and the SO end, it is determinedthat the SOstart and the SOend successfully receive only a part otherthan the part indicated by the LOWER_SN or a part other than the partindicated by the UPPER_SN). The ACK_SN has a predetermined length, andthe predetermined length can be variously defined such as 10 bits, 16bits, or 18 bits.

The E1 field has a length of 1 bit and indicates whether or not theLOWER_SN, the UPPER_SN, the E1 field, and the E2 field follow as inTable 1-14.

TABLE 1-14 E1 field value Description 0 A set of LOWER_SN, E2, UPPER_SN,E1 and E2 does not follow. 1 A set of LOWER_SN, E2, UPPER_SN, E1 and E2follows.

The LOWER_SN may include the lowest SN that has been successfullyreceived. The UPPER_SN may include the highest SN that has not beenreceived. The LOWER_SN and the UPPER_SN may include the SN by variouspredetermined methods to indicate a range of a large number of missedSNs. The LOWER_SN and UPPER_SN have a predetermined length, and thepredetermined length can be variously defined such as 10 bits, 16 bits,or 18 bits. When the first RLC PDU of the RLC layer apparatus of thetransmitting end is missed, the LOWER_SN may be allocated as the samevalue as the UPPER_SN to notify the transmitting end that all the SNssmaller than the UPPER_SN are not received. For example, if the LOWER_SNfield may include a SN 77 and the UPPER_SN includes 77, (SN<=77) may beindicated. When the first RLC PDU is missed, the LOWER_SN and theUPPER_SN may be defined by various methods. Alternatively, another fieldmay be defined.

The E2 field has a length of 1 bit and indicates whether the SOstart andthe SOend follow as in Table 1-15.

TABLE 1-15 E2 field value Description 0 A set of SOstart and SOend doesnot follow for this LOWER_SN or UPPER_SN. 1 A set of SOstart and SOendfollows for this LOWER_SN or UPPER_SN.

The SOstart field indicates a head position of the part when indicatinga part of the LOWER_SN or the UPPER_SN. The head position may beindicated by a byte unit. The SOstart has a predetermined length, andthe predetermined length can be variously defined such as 15 bits, 16bits, and 18 bits.

The SOend field indicates a tail position of the part when indicating apart of the LOWER_SN or the UPPER_SN. The tail position may be indicatedby a byte unit. The SOend has a predetermined length, and thepredetermined length can be variously defined such as 15 bits, 16 bits,and 18 bits.

The 1-3-3-th RLC status reporting method proposed above can be equallyapplied to the NR RLC apparatus of the scenarios such as 1 f-02, 1 f-03,and 1 f-04 in FIGS. 1FA and 1FB.

FIG. 1P is a diagram of an RLC status reporting method, according to anembodiment of the present disclosure.

In FIG. 1P an RLC status report is sent from a receiving side RLC layerapparatus to a transmitting side RLC layer device (assuming a 10 bit RLCSN length).

The receiving side RLC layer device stores the received RLC PDUs in thereceiving buffer and then checks the SN to recognize the SN of the RLCPDU missed during the transmission. If the predetermined condition issatisfied, the receiving side RLC layer apparatus generates an RLCstatus report message and transmits the generated RLC status reportmessage to the transmitting side RLC layer apparatus. The RLC statusreport message includes information on the RLC PDU reception state ofthe receiving side RLC layer apparatus, and the transmitting side RLClayer apparatus identifies the RLC PDU successfully transmitted and theRLC PDU failed to transmit, through the RLC status report message. TheRLC status report message may be written as 1 p-05 in FIG. 1P. The RLCstatus report message includes one ACK_SN or a set of one ACK_SN and oneor more NACK_SN, E1, E2, and E3 fields. It is indicated by the E1 fieldwhether there are the set of NACK_SN, E1, E2, and E3 fields. The E1field indicates whether a set of one NACK_SN field, the E1 field, the E2field, and the E3 field follow, and the E2 field indicates whether ornot SOstart and SOend fields indicating a part of the NACK_SN follow.The E3 field indicates whether there are N (number of missing RLC PDUs)fields indicating how many SNs above (larger) or below (smaller) fromthe SN indicated by the NACK_SN are missed. The N field is a fieldindicating how many SNs above (having a larger SN) or below (having asmaller SN) from the SN indicated by the NACK_SN are missed.

The ACK_SN field may include the next SN of the highest SN among the SNsof RLC PDUs that have successfully been received and the NACK_SN mayinclude the SN that has not been successfully received. When a pluralityof consecutive RLC PDUs are missed, the highest SN that has not beenreceived or the lowest SN that has not been received can be included inthe NACK_SN in order to use NACK_SN together with the N field, and the Nfield may include the number of missed SNs. The NACK_SN and N fields naybe defined and applied by various other methods to indicate a number ofRLC PDUs that have been missed consecutively. That is, as an example,the RLC apparatus of the receiving end may request the retransmission tothe RLC apparatus of the transmitting end since the RLC PDUscorresponding to all SNs between 2<SN<=8 as the NACK_SN=8 and N=6. Asanother example, the transmitting side RLC layer apparatus transmits RLCPDU 5 to RLC PDU 80 at any time, and the receiving side RLC layerapparatus receives only RLC PDU 5, RLC PDU 78, RLC PDU 79, and RLC PDU80 and stores the received RLC PDU 5, RLC PDU 78, RLC PDU 79, and RLCPDU 80 in the receiving buffer. If the RLC status report messagegeneration condition is satisfied at any time, the receiving side RLClayer apparatus generates the RLC status report message. The ACK_SNfield of the RLC status report message may include the SN 81, theNACK_SN field may include the SN 6, and another NACK_SN field mayinclude 69 in the N field together with the SN 8 (6, 8<=SN<=77). Thetransmitting side RLC layer apparatus receiving the RLC status reportmessage determines that the RLC PDU having a SN lower than the lowestNACK_SN, that is, the RLC PDUs having a SN lower than 6 is successfullytransmitted and discards it in a retransmitting buffer. In addition,PDCP SDUs mapped to the RLC PDUs having a SN lower than 6 among the PDCPSDUs stored in the transmission buffer is also discarded. Thetransmitting side RLC layer apparatus retransmits the RLC PDU 6 to RLCPDU 8 to RLC PDU 77 reporting that the receiving side RLC layerapparatus has not received.

The RLC layer apparatus transmits the RLC PDU with the SN, and checkswhether the transmitted RLC PDU succeeds based on the RLC status reportmessage and retransmits the RLC PDU, thereby ensuring reliabletransmission/reception.

By receiving a general RLC status report message, the transmitting sideRLC layer apparatus acquires the following two pieces of informationlargely.

Identify RLC PDU failed in transmission

Identify RLC PDU succeeded in transmission

It is recognized which RLC PDU to retransmit in the future byidentifying the RLC PDU failing to transmit, and it determines which RLCPDU or PDCP SDU of RLC PDUs or PDCP SDUs stored in the retransmissionbuffer and the transmission buffer is discarded.

The fields applied to the RLC status reporting method for the presentdisclosure are as follows.

The D/C field has a length of 1 bit and indicates whether the RLC PDU isan RLC data PDU or an RLC control PDU as in Table 1-16.

TABLE 1-16 D/C field value Description 0 Control PDU 1 Data PDU

The CPT field has a length of 1 bit and indicates a kind of RLC controlPDU as in Table 1-17.

TABLE 1-17 CPT field value Description 000 STATUS PDU 001-111 Reserved(PDUs with this coding will be discarded by the receiving entity forthis release of the protocol)

ACK_SN indicates the next SN of the RLC PDU that has not yet beenreceived and a SN that is not reported as missed in the RLC statusreport. Upon receiving the RLC status report at the transmitting end, itis determined that the SN indicated by the ACK_SN is not included, theSNs indicated by the NACK_SN are not included, the SNs included in therange indicated by the NACK_SN and the N field are not included, and theSN smaller than the ACK_SN has been received successfully (when theNACK_SN is indicated together with the SOstart and the SOend, it isdetermined that the SOstart and the SOend successfully receive only apart other than the part indicated by the NACK_SN). The ACK_SN has apredetermined length, and the predetermined length can be variouslydefined such as 10 bits, 16 bits, or 18 bits.

The E1 field has a length of 1 bit and indicates whether or not theLOWER_SN, the UPPER_SN, the E1 field, and the E2 field follow as inTable 1-18.

TABLE 1-18 E1 field value Description 0 A set of NACK_SN, E1, E2, and E3does not follow. 1 A set of NACK_SN, E1, E2, and E3 follows.

The NACK_SN may include the SN that has not been received. When aplurality of consecutive RLC PDUs are missed, the highest SN that hasnot been received or the lowest SN that has not been received can beincluded in the NACK_SN in order to use NACK_SN together with the Nfield, and the N field may include the number of missed SNs. The NACK_SNand N fields may be defined and applied by various other methods toindicate a number of RLC PDUs that have been missed consecutively. TheNACK_SN has a predetermined length, and the predetermined length can bevariously defined such as 10 bits, 16 bits, or 18 bits.

The N field is a field indicating how many SNs above (having a largerSN) or below (having a smaller SN) from the SN indicated by the NACK_SNare missed.

The E2 field has a length of 1 bit and indicates whether the SOstart andthe SOend follow as in Table 1-19.

Table 1-19 E2 field value Description 0 A set of SOstart and SOend doesnot follow for this LOWER_SN or UPPER_SN. 1 A set of SOstart and SOendfollows for this LOWER_SN or UPPER_SN.

The E3 field indicates whether there are N (number of missing RLC PDUs)fields indicating how many SNs above (larger) or below (smaller) fromthe SN indicated by the NACK_SN are missed as in Table 1-20.

TABLE 1-20 E3 field value Description 0 N does not follow for thisNACK_SN. 1 N follows for this NACK_SN.

The SOstart field indicates a head position of the part when indicatinga part of the NACK_SN. The head position may be indicated by a byteunit. The SOstart has a predetermined length, and the predeterminedlength can be variously defined such as 15 bits, 16 bits, and 18 bits.

The SOend field indicates a tail position of the part when indicating apart of the NACK_SN. The tail position may be indicated by a byte unit.The SOend has a predetermined length, and the predetermined length canbe variously defined such as 15 bits, 16 bits, and 18 bits.

The RLC status reporting method proposed above can be equally applied tothe NR RLC apparatus of 1 f-02, 1 f-03, and 1 f-04 in FIGS. 1FA and 1FB.

FIG. 1Q is a flowchart of a method of the terminal.

In FIG. 1Q, the terminal receives a packet from the higher layer (atstep 1 q-05) and configures an RLC header (at step 1 q-10) to generatethe received packet as the RLC PDU. When configuring the RLC header, oneof the previously described methods for configuring the RLC header canbe used to configure the RLC header (at step 1 q-15). The generated RLCPDU is transferred to a lower layer (at step 1 q-20). The operation ofthe terminal may equally apply to the NR RLC apparatus of the 1 f-02, 1f-03, 1 f-04 in FIGS. 1FA and 1FB.

FIG. 1R is a diagram of the terminal, according to an embodiment of thepresent disclosure.

Referring to FIG. 1R, the terminal includes a radio frequency (RF)processor 1 r-10, a baseband processor 1 r-20, a memory 1 r-30, and acontroller 1 r-40.

The RF processor 1 r-10 serves to transmit and receive a signal througha radio channel, such as band conversion and amplification of a signal.That is, the RF processor 1 r-10 up-converts a baseband signal providedfrom the baseband processor 1 r-20 into an RF band signal and thentransmits the RF band signal through an antenna and down-converts the RFband signal received through the antenna into the baseband signal. TheRF processor 1 r-10 may include a transmitting filter, a receivingfilter, an amplifier, a mixer, an oscillator, a digital to analogconverter (DAC), an analog to digital converter (ADC), or the like. FIG.1R illustrates only one antenna but the terminal may include a pluralityof antennas. The RF processor 1 r-10 may include a plurality of RFchains. The RF processor 1 r-10 may perform beamforming. For thebeamforming, the RF processor 1 r-10 may adjust a phase and a size ofeach of the signals transmitted and received through a plurality ofantennas or antenna elements. In addition, the RF processor may performMIMO and may receive a plurality of layers when performing a MIMOoperation. The RF processor 1 r-10 may perform reception beam sweepingby appropriately configuring a plurality of antennas or antenna elementsunder the control of the controller or adjust a direction and a beamwidth of the reception beam so that the reception beam is resonated withthe transmission beam.

The baseband processor 1 r-20 performs a conversion function between abaseband signal and a bit string according to a physical layer standardof a system. When data is transmitted, the baseband processor 1 r-20generates complex symbols by coding and modulating a transmitted bitstring. Further, when data is received, the baseband processor 1 r-20recovers the received bit string by demodulating and decoding thebaseband signal provided from the RF processor 1 r-10. According to theOFDM scheme, when data is transmitted, the baseband processor 1 r-20generates the complex symbols by coding and modulating the transmittingbit string, maps the complex symbols to sub-carriers, and then performsan inverse fast Fourier transform (IFFT) operation and a cyclic prefix(CP) insertion to configure the OFDM symbols. Further, when data arereceived, the baseband processor 1 r-20 divides the baseband signalprovided from the RF processor 1 r-10 in an OFDM symbol unit andrecovers the signals mapped to the sub-carriers by a fast Fouriertransform (FFT) operation and then recovers the received bit string bythe modulation and decoding.

The baseband processor 1 r-20 and the RF processor 1 r-10 transmit andreceive a signal as described above. The baseband processor 1 r-20 andthe RF processor 1 r-10 may be called a transmitter, a receiver, atransceiver, or a communication unit. At least one of the basebandprocessor 1 r-20 and the RF processor 1 r-10 may include a plurality ofcommunication modules to support a plurality of different RATs. Further,at least one of the baseband processor 1 r-20 and the RF processor 1r-10 may include different communication modules to process signals indifferent frequency bands. The different wireless access technologiesmay include an LTE network, an NR network, and the like. Further,different frequency bands may include a super high frequency (SHF) (forexample, 2.5 GHz, 5 GHz) band, a millimeter wave (for example, 60 GHz)band.

The memory 1 r-30 stores data such as basic programs, applicationprograms, and configuration information for the operation of theterminal. Further, the memory 1 r-30 provides the stored data accordingto the request of the controller 1 r-40.

The controller 1 r-40 controls the overall operations of the terminal.The controller 1 r-40 transmits and receives a signal through thebaseband processor 1 r-20 and the RF processor 1 r-10. Further, thecontroller 1 r-40 records and reads data in and from the memory 1 r-40.The controller 1 r-40 may include at least one processor, and mayinclude a communication processor (CP) performing a control forcommunication, an application processor (AP) controlling a higher layersuch as the application programs, and a multiple connection processor 1r-42 controlling connections between multiple nodes.

FIG. 1S is a diagram of a base station or a TRP (transmission andreception point) in a wireless communication system, according to anembodiment of the present disclosure.

As illustrated in FIG. 1S, the base station is configured to include anRF processor 1 s-10, a baseband processor 1 s-20, a communication unit 1s-30, a memory 1 s-40, and a controller 1 s-50.

The RF processor 1 s-10 serves to transmit and receive a signal througha radio channel, such as band conversion and amplification of a signal.That is, the RF processor 1 s-10 up-converts a baseband signal providedfrom the baseband processor 1 s-20 into an RF band signal and thentransmits the RF band signal through an antenna and down-converts the RFband signal received through the antenna into the baseband signal. TheRF processor 1 s-10 may include a transmitting filter, a receivingfilter, an amplifier, a mixer, an oscillator, a DAC, an ADC, or thelike. FIG. 1S illustrates only one antenna but the first access node mayinclude a plurality of antennas. The RF processor 1 s-10 may include aplurality of RF chains. Further, the RF processor 1 s-10 may perform thebeamforming. For the beamforming, the RF processor 1 s-10 may adjust aphase and a size of each of the signals transmitted/received through aplurality of antennas or antenna elements. The RF processor 1 s-10 mayperform a downward MIMO operation by transmitting one or more layers.

The baseband processor 1 s-20 performs a conversion function between thebaseband signal and the bit string according to the physical layerstandard of the first radio access technology. When data is transmitted,the baseband processor 1 s-20 generates complex symbols by coding andmodulating a transmitted bit string. Further, when data is received, thebaseband processor 1 s-20 recovers the received bit string bydemodulating and decoding the baseband signal provided from the RFprocessor 1 s-10. According to the OFDM scheme, when data istransmitted, the baseband processor 1 s-20 generates the complex symbolsby coding and modulating the transmitting bit string, maps the complexsymbols to the sub-carriers, and then performs the IFFT operation andthe CP insertion to construct the OFDM symbols. When data is received,the baseband processor 1 s-20 divides the baseband signal provided fromthe RF processor 1 s-10 in the OFDM symbol unit and recovers the signalsmapped to the sub-carriers by the FFT operation and then recovers thereceiving bit string by the modulation and decoding. The basebandprocessor 1 s-20 and the RF processor 1 s-10 transmit and receive asignal as described above. Therefore, the baseband processor 1 s-20 andthe RF processor 1 s-10 may be called a transmitter, a receiver, atransceiver, or a communication unit.

The communication unit 1 s-30 provides an interface for performingcommunication with other nodes within the network.

The memory 1 s-40 stores data such as basic programs, applicationprograms, and setting information for the operation of the main basestation. In particular, the memory 1 s-40 may store the information onthe bearer allocated to the accessed terminal, the measured resultsreported from the accessed terminal, etc. The memory 1 s-40 may storeinformation that is a determination criterion on whether to provide amultiple connection to the terminal or stop the multiple connection tothe terminal. Further, the memory 1 s-40 provides the stored dataaccording to the request of the controller 1 s-50.

The controller 1 s-50 controls the general operations of the main basestation. The controller 1 s-50 transmits/receives a signal through thebaseband processor 1 s-20 and the RF processor 1 s-10 or thecommunication unit 1 s-30. Further, the controller 1 s-50 records andreads data in and from the memory 1 s-40. For this purpose, thecontroller 1 s-50 may include at least one processor and/or a multipleconnection processor 1 s-52 controlling connections between multiplenodes.

FIG. 2A is a diagram of an LTE system, according to an embodiment of thepresent disclosure.

As illustrated in FIG. 1A, a RAT of an LTE system is configured toinclude next generation base stations (ENB, Node B, or base station) 2a-05, 2 a-10, 2 a-15, and 2 a-20, an MME 2 a-25, and a S-GW 2 a-30. UEor terminal 2 a-35 accesses an external network through the ENBs 2 a-05to 2 a-20 and the S-GW 2 a-30.

The ENBs 2 a-05 to 2 a-20 correspond to the existing node B of the UMTSsystem. The ENB is connected to the UE 2 a-35 through a radio channeland performs more complicated role than the existing node B. In the LTEsystem, in addition to a real-time service like a VoIP through theinternet protocol, all the user traffics are served through a sharedchannel and therefore an apparatus for collecting and scheduling statusinformation such as a buffer status, an available transmission powerstatus, and a channel state of the terminals is required. The ENBs 2a-05 to 2 a-20 take charge of the collecting and scheduling statusinformation. One ENB generally controls a plurality of cells. Forexample, to implement a transmission rate of 100 Mbps, the LTE systemuses, as a RAT, OFDM in, for example, a bandwidth of 20 MHz. Further, anAMC scheme for determining a modulation scheme and a channel coding ratedepending on a channel status of the terminal is applied. The S-GW 2a-30 is an apparatus for providing a data bearer and generates orremoves the data bearer according to the control of the MME 2 a-25. TheMME is an apparatus for performing a mobility management function forthe terminal and various control functions and is connected to aplurality of base station.

FIG. 2B is a diagram of a radio protocol structure in the LTE system.

The radio protocol of the LTE system is configured to include PDCPs 2b-05 and 2 b-40, RLCs 2 b-10 and 2 b-35, and medium access controls(MACs 2 b-15 and 2 b-30 in the terminal and the ENB, respectively. ThePDCPs 2 b-05 and 2 b-40 control operations such as IP headercompression/decompression. The main functions of the PDCP are summarizedas follows.

Header compression and decompression function (Header compression anddecompression: ROHC only)

Transfer of user data

In-sequence delivery function (In-sequence delivery of upper layer PDUsat PDCP re-establishment procedure for RLC AM)

Reordering function (For split bearers in DC (only support for RLC AM):PDCP PDU routing for transmission and PDCP PDU reordering for reception)

Duplicate detection function (Duplicate detection of lower layer SDUs atPDCP re-establishment procedure for RLC AM)

Retransmission function (Retransmission of PDCP SDUs at HO and, forsplit bearers in DC, of PDCP PDUs at PDCP data-recovery procedure, forRLC AM)

Ciphering and deciphering function (Ciphering and deciphering)

Timer-based SDU discard function (Timer-based SDU discard in uplink)

The RLCs 2 b-10 and 2 b-35 reconfigures the PDCP PDU to an appropriatesize to perform the ARQ operation or the like. The main functions of theRLC are summarized as follows.

Data transfer function (Transfer of upper layer PDUs)

ARQ function (Error Correction through ARQ (only for AM data transfer))

Concatenation, segmentation, reassembly functions (Concatenation,segmentation and reassembly of RLC SDUs (only for UM and AM datatransfer))

Re-segmentation function (Re-segmentation of RLC data PDUs (only for AMdata transfer))

Reordering function (Reordering of RLC data PDUs (only for UM and AMdata transfer))

Duplicate detection function (Duplicate detection (only for UM and AMdata transfer))

Error detection function (Protocol error detection (only for AM datatransfer))

RLC SDU discard function (RLC SDU discard (only for UM and AM datatransfer))

RLC re-establishment function (RLC re-establishment)

The MACs 2 b-15 and 2 b-30 are connected to several RLC layerapparatuses configured in one terminal and perform multiplexing RLC PDUsinto an MAC PDU and demultiplexing the RLC PDUs from the MAC PDU. Themain functions of the MAC are summarized as follows.

Mapping function (Mapping between logical channels and transportchannels)

Multiplexing/demultiplexing function (Multiplexing/demultiplexing of MACSDUs belonging to one or different logical channels into/from TBsdelivered to/from the physical layer on transport channels)

Scheduling information reporting function (Scheduling informationreporting)

HARQ function (Error correction through HARQ)

Priority handling function between logical channels (Priority handlingbetween logical channels of one UE)

Priority handling function between terminals (Priority handling betweenUEs by means of dynamic scheduling)

MBMS service identification function (MBMS service identification)

Transport format selection function (Transport format selection)

Padding function (Padding)

Physical layers 2 b-20 and 2 b-25 perform channel-coding and modulatinghigher layer data, making the higher layer data as an OFDM symbol andtransmitting them to a radio channel, or demodulating andchannel-decoding the OFDM symbol received through the radio channel andtransmitting the demodulated and channel-decoded OFDM symbol to thehigher layer.

FIG. 2C is a diagram of a next generation mobile communication system,according to an embodiment of the present disclosure.

A RAN of a next generation mobile communication system (hereinafterreferred to as NR or 5G) is configured to include a next generation basestation (NR node B, hereinafter NR gNB or NR base station) 2 c-10 and anNR CN 2 c-05. The user terminal (NR UE or UE) 8 c-15 accesses theexternal network through the NR gNB 2 c-10 and the NR CN 2 c-05.

In FIG. 2C, the NR gNB 2 c-10 corresponds to an eNB of the existing LTEsystem. The NR gNB is connected to the NR UE 2 c-15 via a radio channeland may provide a service superior to the existing node B. In the nextgeneration mobile communication system, since all user traffics areserved through a shared channel, an apparatus for collecting stateinformation such as a buffer state, an available transmission powerstate, and a channel state of the UEs to perform scheduling is required.The NR NB 2 c-10 may serve as the device. One NR gNB generally controlsa plurality of cells. In order to realize high-speed data transmissioncompared with the current LTE, the NR gNB may have an existing maximumbandwidth or more, and may be additionally incorporated into abeam-forming technology may be applied by using OFDM as a RAT. An AMCscheme for determining a modulation scheme and a channel coding ratedepending on a channel status of the terminal is applied. The NR CN 2c-05 may perform functions such as mobility support, bearer setup, QoSsetup, and the like. The NR CN is a device for performing a mobilitymanagement function for the terminal and various control functions andis connected to a plurality of base stations. In addition, the nextgeneration mobile communication system can interwork with the existingLTE system, and the NR CN is connected to the MME 2 c-25 through thenetwork interface. The MME is connected to the eNB 2 c-30 which is theexisting base station.

FIG. 2D is a diagram of a radio protocol structure of a next generationmobile communication system, according to an embodiment of the presentdisclosure.

The radio protocol of the next generation mobile communication system isconfigured to include NR PDCPs 2 d-05 and 2 d-40, NR RLCs 2 d-10 and 2d-35, and NR MACs 2 d-15 and 2 d-30 in the terminal and the NR basestation. The main functions of the NR PDCPs 2 d-05 and 2 d-40 mayinclude some of the following functions.

Header compression and decompression function (Header compression anddecompression: ROHC only)

Transfer of user data

In-sequence delivery function (In-sequence delivery of upper layer PDUs)

Reordering function (PDCP PDU reordering for reception)

Duplicate detection function (Duplicate detection of lower layer SDUs)

Retransmission function (Retransmission of PDCP SDUs)

Ciphering and deciphering function (Ciphering and deciphering)

Timer-based SDU discard function (Timer-based SDU discard in uplink)

In this case, the reordering function of the NR PDCP apparatus is forrearranging PDCP PDUs received in a lower layer in order based on a PDCPSN and may include a function of transferring data to a higher layer inthe rearranged order, a function of recording PDCP PDUs lost by thereordering, a function of reporting a state of the lost PDCP PDUs to atransmitting side, and a function of requesting a retransmission of thelost PDCP PDUs.

The main functions of the NR RLCs 2 d-10 and 2 d-35 may include some ofthe following functions.

Data transfer function (Transfer of upper layer PDUs)

In-sequence delivery function (In-sequence delivery of upper layer PDUs)

Out-of-sequence delivery function (Out-of-sequence delivery of upperlayer PDUs)

ARQ function (Error correction through HARQ)

Concatenation, segmentation, reassembly function (Concatenation,segmentation and reassembly of RLC SDUs)

Re-segmentation function (Re-segmentation of RLC data PDUs)

Reordering function (Reordering of RLC data PDUs)

Duplicate detection function (Duplicate detection)

Error detection function (Protocol error detection)

RLC SDU discard function (RLC SDU discard)

RLC re-establishment function (RLC re-establishment)

In the above description, the in-sequence delivery function of the NRRLC apparatus is for delivering RLC SDUs received from a lower layer toa higher layer in order, and may include a function of reassembling andtransferring an original one RLC SDU which is divided into a pluralityof RLC SDUs and received, a function of rearranging the received RLCPDUs based on the RLC SN or the PDCP SN, a function of recording the RLCPDUs lost by the reordering, a function of reporting a state of the lostRLC PDUs to the transmitting side, a function of requesting aretransmission of the lost RLC PDUs, a function of transferring only theSLC SDUs before the lost RLC SDU to the higher layer in order when thereis the lost RLC SDU, a function of transferring all the received RLCSDUs to the higher layer before a predetermined timer starts if thetimer expires even if there is the lost RLC SDU, or a function oftransferring all the RLC SDUs received to the higher layer if thepredetermined timer expires even if there is the lost RLC SDU.

The out-of-sequence delivery function of the NR RLC apparatus is fordirectly delivering the RLC SDUs received from the lower layer to thehigher layer regardless of order, and may include a function ofreassembling and transferring an original one RLC SDU which is dividedinto several RLC SDUs and received, and a function of storing the RLC SNor the PDCP SP of the received RLC PDUs and arranging it in order torecord the lost RLC PDUs.

The NR MACs 2 d-15 and 2 d-30 may be connected to several NR RLC layerapparatuses configured in one terminal, and the main functions of the NRMAC may include some of the following functions.

Mapping function (Mapping between logical channels and transportchannels)

Multiplexing and demultiplexing function (Multiplexing/demultiplexing ofMAC SDUs)

Scheduling information reporting function (Scheduling informationreporting)

HARQ function (Error correction through HARQ)

Priority handling function between logical channels (Priority handlingbetween logical channels of one UE)

Priority handling function between terminals (Priority handling betweenUEs by means of dynamic scheduling)

MBMS service identification function (MBMS service identification)

Transport format selection function (Transport format selection)

Padding function (Padding)

The NR PHY layers 2 d-20 and 2 d-25 may perform an operation ofchannel-coding and modulating higher layer data, making the higher layerdata as an OFDM symbol and transmitting them to a radio channel, ordemodulating and channel-decoding the OFDM symbol received through theradio channel and transmitting the demodulated and channel-decoded OFDMsymbol to the higher layer.

FIGS. 2EA and 2EB are diagrams of the terminal that receives servicesthrough an LTE base station and an NR base station in the nextgeneration mobile communication system, according to an embodiment ofthe present disclosure.

In FIGS. 2EA and 2EB, 2 e-01 shows that the terminal is served from theNR base station, 2 e-02 shows that the LTE base station is the master(MeNB) in the 3C type LTE base station-NR base station interworking, 2e-03 shows that the NR base station is the master (MeNB) in the 3C typeLTE base station-NR base station interworking, 2 e-04 shows that the NRbase station is the master (MeNB) in the 3C type NR base station-NR basestation interworking, 2 e-05 shows a 2a type LTE-base station-NR basestation interworking, and 2 e-06 shows a 2a type NR base station-NR basestation interworking.

FIG. 2F is a diagram of a method for processing a data packet inadvance, according to an embodiment of the present disclosure.

In 2 e-01, 2 e-02, 2 e-03, 2 e-04, 2 e-05, and 2 e-06 of FIGS. 2EA and2EB, when receiving the IP packet 2 f-05 from a higher layer on a userplane layer, the NR base station or the terminal of the next generationmobile communication systems may process the received package inadvance. The processing refers to processing the IP packet to the PDCPPDU 2 f-10 of the PDCP layer, the RLC PDU 2 f-15 of the RLC layer, orthe MAC SDU 2 f-20 together with the MAC subheader of the MAC layer inadvance.

FIG. 2G is a diagram illustrating problems that may occur by a timer(e.g., PDCP discard timer) maintained at a PDCP layer.

In FIG. 2G, when the IP packets are received by the PDCP layer, the PDCPlayer may maintain one timer for each IP packet. The timer may representthe expiration date of the corresponding packet, and if the timerexpires, the corresponding packet is discarded since the expiration dateof the packet expires. For example, it is assumed that the timer for theIP packet 4 expires. If the IP packet 4 is processed in the PDCP layer 2g-05 in advance to be the PDCP PDU, since the expiration date of thecorresponding IP packet has expired, the corresponding PDCP PDU shouldbe discarded. Therefore, the PDCP SN 3 2 g-15 is discarded. The PDCPlayer of the receiving end may not know whether the discarded PDCP SN 3is missed during the transmission or is discarded since the timer hasexpired. Therefore, the receiving end waits for the PDCP SN 3 to beretransmitted, thereby causing a transmission delay. If the IP packet 4is processed in the PDCP layer in advance and transmitted to the RLClayer 2 g-20 and processed in the RLC layer in advance to be the RLC PDU2 g-25, the RLC PDU should be discarded. In this case, the RLC SN 3 isdiscarded. Therefore, the RLC layer of the receiving end may not knowwhether the RLC SN 3 is missed or discarded during the transmission andtherefore continuously waits, such that the window stalling problemoccurs and the normal RLC ARQ operation may not be performed. Theproblem may occur when the PDCP SN is reused in the RLC and the RLC SNis not used in the RLC layer, in other words, when only one SN is usedduring the whole data processing.

FIGS. 2HA, 2HB, and 2HC are diagrams of a 2-1-th packet that hasexpired, according to an embodiment of the present disclosure.

In FIGS. 2HA, 2HB, and 2HC, the 2-1-th expired packet processing methodfor the present disclosure may be divided into the operations of thePDCP layer, the RLC layer, and the MAC layer as follows.

Operation of PDCP Layer

In the PDCP layer, the timer is driven for each packet entering the PDCPlayer. The timer may be a timer representing the expiration date of eachtimer, and each timer value may be indicated as the RRC message by thebase station. If the timer has expired, the following operations areperformed.

The timer has expired,

if the 1-1-th condition is satisfied, the 1-1-th method is performed,

if the 1-2-th condition is satisfied, the 1-2-th method is performed,and

if the 1-3-th condition is satisfied, the 1-3-th method is performed.

The 1-1-th condition is a case in which a packet corresponding to theexpired timer is not yet processed in the PDCP layer and is stored in apacket or PDCP SDU 2 h-11.

The 1-2-th condition is a case in which the packet corresponding to anexpired timer is processed in the PDCP layer in advance and stored inthe PDCP PDU and not yet transmitted to the RLC layer 2 h-12.

The 1-3-th condition is a case in which the packet corresponding to anexpired timer is processed in the PDCP layer in advance and stored inthe PDCP PDU and transmitted to the RLC layer in advance 2 h-13.

The 1-1-th method is a method for discarding a packet or a PDCP SDUstored in the PDCP layer 2 h-16.

The 1-2-th method is a method for discarding the packet or the PDCP SDUstored in the PDCP layer, discarding only a payload of the PDCP PDUcorresponding to the packet, and transmitting the PDCP header withoutdiscarding the PDCP header 2 h-17, and only the PDCP header istransmitted to the RLC layer.

The 1-3-th method is a method for discarding a packet or a PDCP SDUstored in the PDCP layer and transmitting and notifying an indication ofinformation on a packet having the expired timer to the RLC layer 2h-18.

Operation of RLC Layer

The RLC layer stores the PDCP PDUs received from the PDCP layer and mayprocess the RLC PDUs in advance. If the RLC layer receives an indicationof information on the expired packet from the PDCP layer, the RLC layerperforms the following operations.

The RLC layer receives the indication of the information on the expiredpacket from the PDCP layer,

if the 2-1-th condition is satisfied, the 2-1-th method is performed,

if the 2-2-th condition is satisfied, the 2-2-th method is performed,and

if the 2-3-th condition is satisfied, the 2-3-th method is performed.

The 2-1-th condition is a case in which a packet corresponding to theexpired timer is transmitted to the RLC layer, not yet processed, andstored in PDCP SDU (RLC SDU) 2 h-21.

The 2-2 condition is a case in which the packet corresponding to anexpired timer is transmitted to the RLC layer, processed in advance tobe stored in the PDCP layer, and is not yet transmitted to the RLC layer2 h-22.

The 2-3 condition is a case in which the packet corresponding to anexpired timer is transmitted to the RLC layer, processed in advance tobe stored in the RLC layer, and is transmitted to the RLC layer inadvance 2 h-23.

The 2-1-th method is a method for discarding only the payload of thePDCP PDU (RLC SDU) stored in the RLC layer corresponding to the expiredpacket and transmitting the PDCP header without discarding the PDCPheader 2 h-26, attaching only the PDCP header to the RLC header andtransmitting it to the MAC layer.

The 2-2-th method is a method for discarding only the payload of thePDCP PDU of the RLC SDU processed and stored in the RLC layer andtransmitting the RLC header and the PDCP header without discarding theRLC header and the PDCP header 2 h-27, and transmitting only the PDCPheader and RLC header to the MAC layer.

The 2-3-th method is a method for discarding only the payload of thePDCP PDU of the RLC PDU processed in the RLC layer corresponding to theexpired packet and stored in the retransmission buffer and notdiscarding the RLC header and the PDCP header 2 h-28 and transmittingand notifying the indication of the information on the packet having theexpired timer to the MAC layer 2 h-28.

Operation of MAC layer

The MAC layer stores the RLC PDU received from the RLC layer and mayperform the processing with the MAC subheader and the MAC PDU inadvance. If the MAC layer receives an indication of information on theexpired packet from the RLC layer, the RLC layer performs the followingoperations.

The MAC layer receives the indication of the information on the expiredpacket from the RLC layer,

if the 3-1-th condition is satisfied, the 3-1-th method is performed,

if the 3-2-th condition is satisfied, the 3-2-th method is performed,and

if the 3-3-th condition is satisfied, the 3-3-th method is performed.

The 3-1-th condition refers to a case in which a packet corresponding tothe expired timer is transmitted to the MAC layer, not yet processed,and stored in RLC PDU (MAC SDU) 2 h-31.

The 3-2 condition is a case in which the packet corresponding to theexpired timer is transmitted to the MAC layer, processed in advance tobe stored in the MAC subheader and the MAC SDU, and is not a part of theMAC PDU 2 h-32.

The 3-3 condition is a case in which the packet corresponding to theexpired timer is transmitted to the MAC layer, processed in advance tobe stored in the MAC subheader and the MAC SDU, and is a part of the MACPDU in advance 2 h-33.

The 3-1-th method is a method for discarding only the payload of thePDCP PDU of the RLC SDU stored in the MAC layer corresponding to theexpired packet and transmitting the PDCP header and the RLC headerwithout discarding the PDCP header and the RLC header 2 h-36, attachingonly the MAC subheader to the PDCP header and the RLC header, andconfigured as the MAC PDU and transmitted.

The 3-2-th method is a method for discarding the MAC subheader and onlythe payload of the PDCP PDU of MAC SDU (RLC PDU) that are processed andstored in the MAC layer corresponding to the expired packet andtransmitting the RLC header and the PDCP header without discarding theRLC header and the PDCP header 2 h-37, and newly update the MACsubheader corresponding to the PDCP header and the RLC header, andconfigured as the MAC PDU and transmitted (for example, the L field ofthe MAC subheader should be updated if the payload part of the PDCP PDUof the MAC SDU is deleted).

The 3-3-th method does not perform the processing on the packet that isprocessed in the MAC layer in advance to be a part of the MAC PDU 2h-38.

The 2-1-th condition processes the expired packet for discarding only apart corresponding to the expired packet and transmitting only theheaders when the expired packet is processed with the PDCP PDU, the RLCPDU, or the MAC subheader and the MAC SDU in advance, to solve theproblem occurring in FIG. 2G. Since the header is transmitted by themethod as described above, the missing of the SN does not occur in thePDCP layer or the RLC layer due to the expired packet. However, theoverhead may be increased according to the size of the header during thetransmission, and the overhead is insignificant at a high data rate. The2-1-th condition for processing the expired packet may be applied tosolve the problem that may likewise occur in 2 e-01, 2 e-02, 2 e-03, 2e-04, 2 e-05 and 2 e-06 in FIGS. 2EA and 2EB.

When the 2-1-th condition for processing the expired packet is appliedto the transmitting end, the operation at the receiving end is asfollows.

When the MAC PDU is received at the receiving end, it is demultiplexedand transmitted to the RLC layer, and when the segmented segments arepresent, the RLC layer creates a complete RLC SDU (PDCP PDU) andtransmits it to the PDCP layer. When the PDCP PDU is a header onlypacket, the PDCP layer updates the decoding related parameters (e.g.,HFN (Hyper Frame Number), Next_PDCP_TX_SN, etc.) and does not perform adecoding process on the packet including only the headers (the reason isthat there is no information to be transmitted to the higher layerbecause it is the header only information). If the PDCP PDU received bythe PDCP layer is not a packet including only the header but a generaldata packet, the PDCP layer of the receiving end updates the parametersrelated to the decoding (e.g., HFN, Next_PDCP_TX_SN, etc.) and performsthe decoding procedure on the data packet and performs the integrityverification if necessary.

FIGS. 2IA and 2IB are diagrams of a terminal to which the 2-1-thcondition is applied, according to an embodiment of the presentdisclosure.

When a terminal proceeds to step 2 i-10, if the PDCP discard timer onany packet expires in the PDCP layer at step 2 i-05, the terminal 2 i-01proceeds to step 2 i-10 to confirm the processing of the packet. If the1-1-th condition is satisfied, the 1-1-th method is applied in the PDCP(at step 2 i-15), if the 1-2-th condition is satisfied, the 1-2-thmethod is applied in the PDCP (at step 2 i-20), if the 1-3-th conditionis satisfied, the 1-3-th method is applied in the PDCP layer (at step 2i-25), if the 2-1-th condition is satisfied, the 2-1-th method isapplied in the RLC layer (2 i-30), if the 2-2-th condition is satisfied,the 2-2-th method is applied in the RLC layer (at step 2 i-35), if the2-3-th condition is satisfied, the 2-3-th method is applied in the RLClayer (at step 2 i-40), if the 3-1-th condition is satisfied, the 3-1-thmethod is applied in the MAC layer (at step 2 i-45), if the 3-2-thcondition is satisfied, the 3-2-th method is applied in the MAC layer(at step 2 i-50), and if the 3-3-th condition is satisfied, the 3-3-thmethod is applied in the MAC layer (at step 2 i-55).

FIG. 2J is a flowchart of a method of a terminal of a receiving end whenthe 2-1-th condition is applied, according to an embodiment of thepresent disclosure.

When the receiving terminal receives the MAC PDU, it demultiplexes theMAC PDU and transmits the demultiplexed MAC PDU to the RLC layer, andwhen the segmented segments are present, the RLC layer creates acomplete RLC SDU (PDCP PDU) and transmits it to the PDCP layer (at step2 j-05). When the PDCP layer receives the RLC SDU (PDCP PDU) from theRLC layer, it is confirmed whether the PDCP PDU is a header only packet(at step 2 j-10). In the case of the header only packet, the decodingrelated parameters (e.g., HFN, Next_PDCP_TX_SN, etc.) are updated (atstep 2 j-15) and the decoding procedure on the packet including only theheaders is not performed (at step 2 j-20) (i.e., there is no informationto be transmitted to the higher layer because it is the header onlyinformation). If the PDCP PDU received by the PDCP layer is not a packetincluding only the header but a general data packet, the PDCP layer ofthe receiving end updates the decoding related parameters (e.g., HFN,Next_PDCP_TX_SN, etc.) (at step 2 j-25) and performs the decodingprocedure on the data packet and performs the integrity verification ifnecessary (at step 2 j-30).

FIGS. 2KA and 2KB show a 2-2-th packet that has expired, according to anembodiment of the present disclosure.

In FIGS. 2Ka and 2KB, the 2-2-th expired packet processing method may bedivided into the operations of the PDCP layer and the RLC layer asfollows.

Operation of PDCP Layer

In the PDCP layer, the timer is driven for each packet entering the PDCPlayer. The timer may be a timer representing the expiration date of eachtimer, and each timer value may be indicated as the RRC message by thebase station. If the timer has expired, the following operations areperformed.

The timer has expired,

if the 1-1-th condition is satisfied, the 1-1-th method is performed,

if the 1-2-th condition is satisfied, the 1-2-th method is performed,and

if the 1-3-th condition is satisfied, the 1-3-th method is performed.

The 1-1-th condition is a case in which a packet corresponding to theexpired timer is not yet processed in the PDCP layer and is stored in apacket or PDCP SDU 2 k-11.

The 1-2-th condition is a case in which the packet corresponding to anexpired timer is processed in the PDCP layer in advance and stored inthe PDCP PDU and not yet transmitted to the RLC layer 2 k-12.

The 1-3-th condition is a case in which the packet corresponding to anexpired timer is processed in the PDCP layer in advance and stored inthe PDCP PDU and transmitted to the RLC layer in advance 2 k-13.

The 1-1-th method is a method for discarding a packet or a PDCP SDUstored in the PDCP layer 2 k-16.

The 1-2-th method is a method for discarding a packet or a PDCP SDUstored in the PDCP layer and discarding a PDCP PDU corresponding to apacket 2 k-17 (the PDCP header is also discarded).

The 1-3-th method is a method for discarding a packet or a PDCP SDUstored in the PDCP layer and transmitting and notifying an indication ofinformation on a packet having the expired timer to the RLC layer 2k-18.

Operation of RLC layer

The RLC layer stores the PDCP PDUs received from the PDCP layer and mayprocess the RLC PDUs in advance. If the RLC layer receives an indicationof information on the expired packet from the PDCP layer, the RLC layerperforms the following operations.

The RLC layer receives the indication of the information on the expiredpacket from the PDCP layer,

if the 2-1-th condition is satisfied, the 2-1-th method is performed,and

if the 2-2-th condition is satisfied, the 2-2-th method is performed.

The 2-1-th condition is a case in which a packet corresponding to theexpired timer is transmitted to the RLC layer, not yet processed, andstored in PDCP SDU (RLC SDU) 2 k-21.

The 2-2-th condition is a case in which the packet corresponding to anexpired timer is transmitted to the RLC layer, processed in advance tobe stored in the PDCP layer, and is not yet transmitted to the RLC layer2 k-22.

The 2-1-th condition described above is for discarding the PDCP PDUstored in the RLC layer corresponding to the expired packet 2 k-26 (ThePDCP header is also discarded).

The 2-2-th condition described above does not take any action on the RLCPDU stored in the RLC layer corresponding to the expired packet. At thetime of discarding the RLC PDU, a problem may occur in the RLC ARQ ofthe receiving end.

The 2-2-th condition is for discarding the PDCP PDU corresponding to theexpired packet when the expired packet has already been processed withthe PDCP PDU or the RLC PDU and not discarding the RLC PDU, to solve theproblem arising in FIG. 2G. Therefore, although the RLC ARQ problem canbe prevented, the transmission delay may occur in the PDCP layer.However, since the case where the packet expires is rare, the effect ofthe transmission delay may be insignificant. The 2-2-th condition may beapplied to solve the problem that may likewise occur even in 2 e-01, 2e-02, 2 e-03, 2 e-04, 2 e-05 and 2 e-06 in FIGS. 2EA and 2EB.

FIG. 2L is a flowchart of a method of a terminal to which the 2-2-thcondition is applied, according to an embodiment of the presentdisclosure.

When a terminal proceeds to step 2 i-10, if the PDCP discard timer onany packet expires in the PDCP layer (at step 2 l-05), the terminalproceeds to step 2 l-10 to identify the processing of the packet. If the1-1-th condition is satisfied, the 1-1-th method is applied in the PDCPlayer (at step 2 l-15), if 1-2-th condition is satisfied, the 1-2-thmethod is applied in the PDCP layer (at step 2 l-20), if the 1-3-thcondition is satisfied, the 1-3-th method is applied in the PDCP layer(at step 2 l-25), if the 2-1-th condition is satisfied, the 2-1-thmethod is applied in the RLC layer (at step 2 l-30), and if the 2-2-thcondition is satisfied, the 2-2-th method is applied in the RLC layer(at step 2 l-35).

FIG. 2M is a diagram of a PDCP control PDU for explaining a 2-3-thpacket that has expired, according to an embodiment of the presentdisclosure.

FIG. 2M shows an example of a PDCP status report format of a PDCPcontrol PDU using 18 bits as a PDCP SN. The PDCP SNs discarded due tothe expiration of the timer are transferred from the transmitting end tothe receiving end. The PDCP SN may have any bit and may be set in thebase station by the RRC message. As in 2 m-05, the header may have a D/Cfield, a PDU Type field, an R field, a first discarded SN (FDS) field,and a bitmap field. Some or all of these fields or another new field maybe included or defined in the PDCP status report format. The D/C fieldhas a length of 1 bit and can indicate a PDCP control PDU if it has avalue of 0 and indicate a PDCP data PDU if it has a value of 1 as inTable 2-1.

TABLE 2-1 D/C field Description 0 Control PDU 1 Data PDU D/C fieldDescription

The PDU Type field may have a length of 3 bits, and each bit value mayindicate different PDU types as follows. The PDU Type field may have apredetermined different length and may be defined differently toindicate a PDCP status report as in Table 2-2.

TABLE 2-2 PDU type field Description 000 Tx PDCP status report 001-111Reserved

The FDS field may have a length equal to the PDCP SN, and may indicate adiscarded first SN.

The bitmap field may have a predetermined length, and each bit maysequentially indicate whether to discard the SNs are discarded based onthe SN of the FDS field.

The 2-3-th expired packet uses the PDCP status report to transmit theinformation on the packet discarded due to the expiration of the timer(PDCP discard timer). If the PDCP SNs 3, 4, 5, and 6 are discarded dueto the expiration of the timer, the PDCP SNs 3, 4, 5, and 6 arediscarded when the PDCP status report is sent to the PDCP control PDUand is indicated by the FDS field and the bitmap, and may be transmittedto the receiving side. The receiving side receives the PDCP statusreport, confirms the fact that the packets corresponding to the PDCP SNs3, 4, 5 and 6 are not missed but discarded, and does not wait for thePDCP SNs 3, 4, 5 and 6, thereby preventing the transmission delay.

The PDCP status report transmitted in order to indicate the packetdiscarded due to the expiration may be transmitted according to apredetermined criterion. The predetermined conditions may be thefollowing examples.

if the transmitting end transmits more than a predetermined number ofPDCP SNs,

transmission if the predetermined period is satisfied, that is, at eachpredetermined period,

if the PDCP SN discarded due to the expiration is present,

if the PDCP SN discarded due to the expiration is present and thetransmission resource is allocated,

if the retransmission is requested in the PDCP layer of the receivingend,

and/or other reasons.

The PDCP control PDU of the PDCP status report may be located at theheader if necessary when the transmitting end configures the MAC PDU.

FIG. 2N is a flowchart of a method of setting, by a terminal, each layerapparatus in the next generation mobile communication systems of thepresent disclosure.

FIG. 2N also shows a method for setting a connection with a network inwhich a terminal transmits/receives data and configuring apparatuses ofeach layer.

If there is data to be transmitted, a terminal 2 n-01 for which noconnection is currently established performs an RRC connectionestablishment procedure with the LTE base station or the NR base station2 n-02. The terminal 2 n-01 establishes uplink transmissionsynchronization with the base station 2 n-02 through a random accessprocedure and transmits an RRCConnectionRequest message to the basestation (at step 2 n-05). The message includes establishmentCause forconnection with an identifier of the terminal 2 n-01.

The base station 2 n-02 transmits an RRCConnectionSetup message to allowthe terminal 2 n-01 to set the RRC connection (at step 2 n-10). Themessage may store RRC connection configuration information, settinginformation of each layer, and the like. In other words, it may includeconfiguration information on the PHY or NR PHY apparatus, the MAC or NRMAC apparatus, the RLC or NR RLC apparatus, the PDCP or the NR PDCPapparatus, and the information instructing the setting for the specificfunctions among the functions (functions for each layer described inFIG. 2B or 2D) supported by the layer apparatuses. In addition, themessage may include an indication as to whether to use the PDCP discardtimer value to be used in the PDCP apparatus or the header-only packet,an indication as to whether the PDCP control PDU sends the informationon the discarded packet due to the expiration of the timer to the PDCPstatus report, and the like. The RRC connection is also called asignaling radio bearer (SRB) and is used for transmission and receptionof the RRC message that is a control message between the terminal 2 n-01and the base station 2 n-02.

The terminal 2 n-01 establishing the RRC connection transmits anRRCConnetionSetupComplete message to the base station 2 n-02 (at step 2n-15). The base station 2 n-02 transmits an RRCConnectionReconfigurationmessage to the terminal 2 n-01 in order to set up a DRB (at step 2n-20). The configuration information of each layer and the like may bestored in the message. In other words, it may include configurationinformation on the PHY or NR PHY apparatus, the MAC or NR MAC apparatus,the RLC or NR RLC apparatus, the PDCP or the NR PDCP apparatus, and theinformation instructing the setting for the specific functions among thefunctions (functions for each layer described in FIG. 2B or 2D)supported by the layer apparatuses.

In addition, the message may include an indication as to whether to usethe PDCP discard timer value to be used in the PDCP apparatus or theheader-only packet, an indication as to whether the PDCP control PDUsends the information on the discarded packet due to the expiration ofthe timer to the PDCP status report, and the like. In addition, themessage includes the configuration information of the DRB in which userdata are processed, and the terminal 2 n-01 applies the information toset the DRB and set the functions of each layer and transmits anRRCConnectionReconfigurationComplete message to the base station 2 n-02(at step 2 n-25).

If the above procedure is completed, the terminal 2 n-01 transmits andreceives data to and from the base station 2 n-02 (at step 2 n-30).While transmitting and receiving data, the base station 2 n-02 may againtransmit the RRCConnectionReconfiguration message to the terminal 2 n-01(at step 2 n-35), if necessary, and again set the configurationinformation of each layer of the terminal 2 n-01.

In other words, it may include configuration information on the PHY orNR PHY apparatus, the MAC or NR MAC apparatus, the RLC or NR RLCapparatus, the PDCP or the NR PDCP apparatus, and the informationinstructing the setting for the specific functions among the functions(functions for each layer described in FIG. 2B or 2D) supported by thelayer apparatuses.

In addition, the message may include an indication as to whether to usethe PDCP discard timer value to be used in the PDCP apparatus or theheader-only packet, an indication as to whether the PDCP control PDUsends the information on the discarded packet due to the expiration ofthe timer to the PDCP status report, and the like. The message mayinclude the information for configuring the interworking between the LTEbase station (or NR base station) and the NR base station. Theinformation for setting the interworking between the LTE base stationand the NR base station may include information indicating a 3C type ora 2a type, information on each layer apparatus according to each type,and the like. Upon completion of the setting of apparatuses of eachlayer according to the message, the terminal 2 n-01 transmits anRRCConnectionReconfigurationComplete message to the base station 2 n-02(at step 2 n-40).

In the above procedure, if the terminal 2 n-01 receives the PDCP discardtimer value by the RRCConnectionSetup message (at step 2 n-10) or theRRCConnectionReconfiguration message (at steps 2 n-20 and 2 n-35), theterminal 2 n-01 can set the value as a timer value for each packet inthe PDCP layer. If the indicator for the header only packet is receivedin the above messages, the 2-1-th processing of the expired packet canbe applied. If the indicator for the header only packet is not received,the 2-2-th processing of the expired packet can be applied, and if thePDCP control PDU receives an indication as to whether to transmit theinformation on the packet discarded due to the expiration of the timerto the PDCP status report, the 2-3-th processing of the expired packetcan be applied. If the indication for the header only packet is receivedin the messages and the PDCP control PDU receives the indication as towhether to transmit the information on the packet discarded due to theexpiration of the timer to the PCCP status report, both of the 2-2-thand 2-3-th processing of the expired packet can be applied.

FIG. 2O is a diagram of the terminal, according to an embodiment of thepresent disclosure.

Referring to FIG. 2O, the terminal includes an RF processor 2 o-10, abaseband processor 2 o-20, a memory 2 o-30, and a controller 2 o-40including a multiple connection processor 2 o-42.

The RF processor 2 o-10 serves to transmit and receive a signal througha radio channel, such as band conversion and amplification of a signal.That is, the RF processor 2 o-10 up-converts a baseband signal providedfrom the baseband processor 2 o-20 into an RF band signal and thentransmits the RF band signal through an antenna and down-converts the RFband signal received through the antenna into the baseband signal. TheRF processor 2 o-10 may include a transmitting filter, a receivingfilter, an amplifier, a mixer, an oscillator, a DAC, an ADC, or thelike. FIG. 2O illustrates only one antenna but the terminal may includea plurality of antennas. Further, the RF processor 2 o-10 may include aplurality of RF chains. Further, the RF processor 2 o-10 may performbeamforming. The RF processor 2 o-10 may adjust a phase and a size ofeach of the signals transmitted and received through a plurality ofantennas or antenna elements. In addition, the RF processor 2 o-10 mayperform MIMO and may receive a plurality of layers when performing aMIMO operation. The RF processor 2 o-10 may perform reception beamsweeping by appropriately configuring a plurality of antennas or antennaelements under the control of the controller or adjust a direction and abeam width of the reception beam so that the reception beam is resonatedwith the transmission beam.

The baseband processor 2 o-20 performs a conversion function between abaseband signal and a bit string according to a physical layer standardof a system. When data is transmitted, the baseband processor 2 o-20generates complex symbols by coding and modulating a transmitted bitstring. Further, when data is received, the baseband processor 2 o-20recovers the received bit string by demodulating and decoding thebaseband signal provided from the RF processor 2 o-10. According to theOFDM scheme, when data is transmitted, the baseband processor 2 o-20generates the complex symbols by coding and modulating the transmittingbit string, maps the complex symbols to sub-carriers, and then performsan IFFT operation and a CP insertion to construct the OFDM symbols.Further, when data is received, the baseband processor 2 o-20 dividesthe baseband signal provided from the RF processor 2 o-10 in an OFDMsymbol unit and recovers the signals mapped to the sub-carriers by anFFT operation and then recovers the received bit string by themodulation and decoding.

The baseband processor 2 o-20 and the RF processor 2 o-10 transmit andreceive a signal as described above. Therefore, the baseband processor 2o-20 and the RF processor 2 o-10 may be called a transmitter, areceiver, a transceiver, or a communication unit. Further, at least oneof the baseband processor 2 o-20 and the RF processor 2 o-10 may includea plurality of communication modules to support a plurality of differentRATs. Further, at least one of the baseband processor 2 o-20 and the RFprocessor 2 o-10 may include different communication modules to processsignals in different frequency bands. The different wireless accesstechnologies may include an LTE network, an NR network, and the like.Further, different frequency bands may include an SHF (for example: 2.5GHz, 5 GHz) band, a millimeter wave (for example: 60 GHz) band.

The memory 2 o-30 stores data such as basic programs, applicationprograms, and configuration information for the terminal. The memory 2o-30 provides the stored data according to the request of the controller2 o-40.

The controller 2 o-40 controls the overall operations of the terminal.The controller 2 o-40 transmits and receives a signal through thebaseband processor 2 o-20 and the RF processor 2 o-10. The controller 2o-40 records and reads data in and from the memory 2 o-40. Thecontroller 2 o-40 may include at least one processor, a CP performing acontrol for communication and an AP controlling an upper layer such asthe application programs.

FIG. 2P is a diagram of a base station or a TRP in a wirelesscommunication system, according to an embodiment of the presentdisclosure.

The base station is configured to include an RF processor 2 p-10, abaseband processor 2 p-20, a communication unit 2 p-30, a memory 2 p-40,and a controller 2 p-50.

The RF processor 2 p-10 serves to transmit and receive a signal througha radio channel, such as band conversion and amplification of a signal.The RF processor 2 p-10 up-converts a baseband signal provided from thebaseband processor 2 p-20 into an RF band signal and then transmits theRF band signal through an antenna and down-converts the RF band signalreceived through the antenna into the baseband signal. The RF processor2 p-10 may include a transmitting filter, a receiving filter, anamplifier, a mixer, an oscillator, a DAC, an ADC, or the like. FIG. 2Pillustrates only one antenna but the RF processor 2 p-10 may include aplurality of antennas. The RF processor 2 p-10 may include a pluralityof RF chains. The RF processor 2 p-10 may perform beamforming. The RFprocessor 2 p-10 may adjust a phase and a size of each of the signalstransmitted/received through a plurality of antennas or antennaelements. The RF processor 2 p-10 may perform a downward MIMO operationby transmitting one or more layers.

The baseband processor 2 p-20 performs a conversion function between thebaseband signal and the bit string according to the physical layerstandard of the first RAT. When data is transmitted, the basebandprocessor 2 p-20 generates complex symbols by coding and modulating atransmitted bit string. When data is received, the baseband processor 2p-20 recovers the received bit string by demodulating and decoding thebaseband signal provided from the RF processor 2 p-10. According to theOFDM scheme, when data is transmitted, the baseband processor 2 p-20generates the complex symbols by coding and modulating the transmittingbit string, maps the complex symbols to the sub-carriers, and thenperforms the IFFT operation and the CP insertion to construct the OFDMsymbols. When data is received, the baseband processor 2 p-20 dividesthe baseband signal provided from the RF processor 2 p-10 in the OFDMsymbol unit and recovers the signals mapped to the sub-carriers by theFFT operation and then recovers the receiving bit string by themodulation and decoding. The baseband processor 2 p-20 and the RFprocessor 2 p-10 transmit and receive a signal as described above. Thebaseband processor 2 p-20 and the RF processor 2 p-10 may be called atransmitter, a receiver, a transceiver, or a communication unit.

The communication unit 2 p-30 provides an interface for performingcommunication with other nodes within the network.

The memory 2 p-40 stores data such as basic programs, applicationprograms, and setting information for the main base station. Inparticular, the memory 2 p-40 may store the information on the bearerallocated to the accessed terminal, the measured results reported fromthe accessed terminal, etc. Further, the memory 2 p-40 may storeinformation that is a determination criterion on whether to provide amultiple connection to the terminal or stop the multiple connection tothe terminal. Further, the memory 2 p-40 provides the stored dataaccording to the request of the controller 2 p-50.

The controller 2 p-50 controls the general operations of the main basestation. The controller 2 p-50 transmits and receives a signal throughthe baseband processor 2 p-20 and the RF processor 2 p-10 or thecommunication unit 2 p-30. The controller 2 p-50 records and reads datain and from the memory 2 p-40. For this purpose, the controller 2 p-50may include at least one processor.

FIG. 3A is a diagram of a structure of an LTE system, in accordance withan embodiment of the present disclosure.

As illustrated in FIG. 1A, a RAN of an LTE system is configured toinclude next generation base stations (ENB, Node B, or base station) 3a-05, 3 a-10, 3 a-15, and 3 a-20, an MME 3 a-25, and a S-GW 3 a-30. UEor terminal 3 a-35 accesses an external network through the ENBs 3 a-05to 3 a-20 and the S-GW 3 a-30.

In FIG. 3A, the ENBs 3 a-05 to 3 a-20 correspond to the existing node Bof the UMTS system. The ENB is connected to the UE 3 a-35 through aradio channel and performs a more complicated role than the existingnode B. In the LTE system, in addition to a real-time service like aVoIP through the internet protocol, all the user traffics are servedthrough a shared channel and therefore an apparatus for collecting andscheduling status information such as a buffer status, an availabletransmission power status, and a channel state of the terminals isrequired. Here, the ENBs 3 a-05 to 3 a-20 control the collecting andscheduling of the buffer status information. One ENB generally controlsa plurality of cells. For example, to implement a transmission rate of100 Mbps, the LTE system uses, as RAT, OFDM in, for example, a bandwidthof 20 MHz. Further, an AMC scheme determining a modulation scheme and achannel coding rate depending on a channel status of the terminal isapplied. The S-GW 3 a-30 is an apparatus for providing a data bearer andgenerates or removes the data bearer according to the control of the MME3 a-25. The MME is an apparatus for performing a mobility managementfunction for the terminal and various control functions and is connectedto a plurality of base stations.

FIG. 3B is a diagram of a radio protocol structure in the LTE system, inaccordance with an embodiment of the present disclosure.

Referring to FIG. 3B, the radio protocol of the LTE system is configuredto include PDCPs 3 b-05 and 3 b-40, RLCs 3 b-10 and 3 b-35, and MACs 3b-15 and 3 b-30 in the terminal and the ENB, respectively. The PDCPs 3b-05 and 3 b-40 control operations such as IP headercompression/decompression. The main functions of the PDCP are summarizedas follows.

Header compression and decompression function (Header compression anddecompression: ROHC only)

Transfer of user data

In-sequence delivery function (In-sequence delivery of upper layer PDUsat PDCP re-establishment procedure for RLC AM)

Reordering function (For split bearers in DC (only support for RLC AM):PDCP PDU routing for transmission and PDCP PDU reordering for reception)

Duplicate detection function (Duplicate detection of lower layer SDUs atPDCP re-establishment procedure for RLC AM)

Retransmission function (Retransmission of PDCP SDUs at HO and, forsplit bearers in DC, of PDCP PDUs at PDCP data-recovery procedure, forRLC AM)

Ciphering and deciphering function (Ciphering and deciphering)

Timer-based SDU discard function (Timer-based SDU discard in uplink)

The RLCs 3 b-10 and 3 b-35 reconfigure the PDCP PDU to an appropriatesize to perform the ARQ operation or the like. The main functions of theRLC are summarized as follows.

Data transfer function (Transfer of upper layer PDUs)

ARQ function (Error Correction through ARQ (only for AM data transfer))

Concatenation, segmentation, reassembly functions (Concatenation,segmentation and reassembly of RLC SDUs (only for UM and AM datatransfer))

Re-segmentation function (Re-segmentation of RLC data PDUs (only for AMdata transfer))

Reordering function (Reordering of RLC data PDUs (only for UM and AMdata transfer))

Duplicate detection function (Duplicate detection (only for UM and AMdata transfer))

Error detection function (Protocol error detection (only for AM datatransfer))

RLC SDU discard function (RLC SDU discard (only for UM and AM datatransfer))

RLC re-establishment function (RLC re-establishment)

The MACs 3 b-15 and 3 b-30 are connected to several RLC layerapparatuses configured in one terminal and perform multiplexing RLC PDUsinto an MAC PDU and demultiplexing the RLC PDUs from the MAC PDU. Themain functions of the MAC are summarized as follows.

Mapping function (Mapping between logical channels and transportchannels)

Multiplexing/demultiplexing function (Multiplexing/demultiplexing of MACSDUs belonging to one or different logical channels into/from TBsdelivered to/from the physical layer on transport channels)

Scheduling information reporting function (Scheduling informationreporting)

HARQ function (Error correction through HARQ)

Priority handling function between logical channels (Priority handlingbetween logical channels of one UE)

Priority handling function between terminals (Priority handling betweenUEs by means of dynamic scheduling)

MBMS service identification function (MBMS service identification)

Transport format selection function (Transport format selection)

Padding function (Padding)

Physical layers 3 b-20 and 3 b-25 perform channel-coding and modulatinghigher layer data, making the higher layer data as an OFDM symbol andtransmitting them to a radio channel, or demodulating andchannel-decoding the OFDM symbol received through the radio channel andtransmitting the demodulated and channel-decoded OFDM symbol to thehigher layer.

FIG. 3C is a diagram of a next generation mobile communication system,in accordance with an embodiment of the present disclosure.

Referring to FIG. 3C, a RAN of a next generation mobile communicationsystem (e.g., NR or 5G) is configured to include a next generation basestation (NR node B, NR gNB or NR base station) 3 c-10 and an NR CN 3c-05. The user terminal (NR UE or UE) 3 c-15 accesses the externalnetwork through the NR gNB 3 c-10 and the NR CN 3 c-05.

In FIG. 3C, the NR gNB 3 c-10 corresponds to an eNB of the existing LTEsystem. The NR gNB is connected to the NR UE 3 c-15 via a radio channeland may provide a service superior to the existing node B. In the nextgeneration mobile communication system, since all user traffics areserved through a shared channel, an apparatus for collecting stateinformation such as a buffer state, an available transmission powerstate, and a channel state of the UEs to perform scheduling is required.The NR NB 3 c-10 may serve as the device. One NR gNB generally controlsa plurality of cells. In order to realize high-speed data transmissioncompared with the current LTE, the NR gNB may have an existing maximumbandwidth, and may be additionally incorporated into a beam-formingtechnology may be applied by using OFDM as a RAT. Further, an AMC schemedetermining a modulation scheme and a channel coding rate depending on achannel status of the terminal is applied. The NR CN 3 c-05 may performfunctions such as mobility support, bearer setup, QoS setup, and thelike. The NR CN is a device for performing a mobility managementfunction for the terminal and various control functions and is connectedto a plurality of base stations. In addition, the next generation mobilecommunication system can interwork with the existing LTE system, and theNR CN is connected to the MME 3 c-25 through the network interface. TheMME is connected to the eNB 3 c-30 which is the existing base station.

FIG. 3D is a diagram of a radio protocol structure of a next generationmobile communication system, in accordance with an embodiment of thepresent disclosure.

Referring to FIG. 3D, the radio protocol of the next generation mobilecommunication system is configured to include NR PDCPs 3 d-05 and 3d-40, NR RLCs 3 d-10 and 3 d-35, and NR MACs 3 d-15 and 3 d-30 in theterminal and the NR base station. The main functions of the NR PDCPs 3d-05 and 3 d-40 may include some of the following functions.

Header compression and decompression function (Header compression anddecompression: ROHC only)

Transfer of user data

In-sequence delivery function (In-sequence delivery of upper layer PDUs)

Reordering function (PDCP PDU reordering for reception)

Duplicate detection function (Duplicate detection of lower layer SDUs)

Retransmission function (Retransmission of PDCP SDUs)

Ciphering and deciphering function (Ciphering and deciphering)

Timer-based SDU discard function (Timer-based SDU discard in uplink)

In this case, the reordering function of the NR PDCP apparatus is forrearranging PDCP PDUs received in a lower layer in order based on a PDCP(SN and may include a function of transferring data to a higher layer inthe rearranged order, a function of recording PDCP PDUs lost by thereordering, a function of reporting a state of the lost PDCP PDUs to atransmitting side, and a function of requesting a retransmission of thelost PDCP PDUs.

The main functions of the NR RLCs 3 d-10 and 3 d-35 may include some ofthe following functions.

Data transfer function (Transfer of upper layer PDUs)

In-sequence delivery function (In-sequence delivery of upper layer PDUs)

Out-of-sequence delivery function (Out-of-sequence delivery of upperlayer PDUs)

ARQ function (Error correction through HARQ)

Concatenation, segmentation, reassembly function (Concatenation,segmentation and reassembly of RLC SDUs)

Re-segmentation function (Re-segmentation of RLC data PDUs)

Reordering function (Reordering of RLC data PDUs)

Duplicate detection function (Duplicate detection)

Error detection function (Protocol error detection)

RLC SDU discard function (RLC SDU discard)

RLC re-establishment function (RLC re-establishment)

In the above description, the in-sequence delivery function of the NRRLC apparatus is for of delivering RLC SDUs received from a lower layerto a higher layer in order, and may include a function of reassemblingand transferring an original one RLC SDU which is divided into aplurality of RLC SDUs and received, a function of rearranging thereceived RLC PDUs based on the RLC SN or the PDCP SN, a function ofrecording the RLC PDUs lost by the reordering, a function of reporting astate of the lost RLC PDUs to the transmitting side, a function ofrequesting a retransmission of the lost RLC PDUs, a function oftransferring only the SLC SDUs before the lost RLC SDU to the higherlayer in order when there is the lost RLC SDU, a function oftransferring all the received RLC SDUs to the higher layer before apredetermined timer starts if the timer expires even if there is thelost RLC SDU, or a function of transferring all the RLC SDUs receiveduntil now to the higher layer in order if the predetermined timerexpires even if there is the lost RLC SDU.

In this case, the out-of-sequence delivery function of the NR RLCapparatus is for directly delivering the RLC SDUs received from thelower layer to the higher layer regardless of order, and may include afunction of reassembling and transferring an original one RLC SDU whichis divided into several RLC SDUs and received, and a function of storingthe RLC SN or the PDCP SP of the received RLC PDUs and arranging it inorder to record the lost RLC PDUs.

The NR MACs 3 d-15 and 3 d-30 may be connected to several NR RLC layerapparatus configured in one terminal, and the main functions of the NRMAC may include some of the following functions.

Mapping function (Mapping between logical channels and transportchannels)

Multiplexing and demultiplexing function (Multiplexing/demultiplexing ofMAC SDUs)

Scheduling information reporting function (Scheduling informationreporting)

HARQ function (Error correction through HARQ)

Priority handling function between logical channels (Priority handlingbetween logical channels of one UE)

Priority handling function between terminals (Priority handling betweenUEs by means of dynamic scheduling)

MBMS service identification function (MBMS service identification)

Transport format selection function (Transport format selection)

Padding function (Padding)

The NR PHY layers 3 d-20 and 3 d-25 may perform channel-coding andmodulating higher layer data, making the higher layer data as an OFDMsymbol and transmitting them to a radio channel, or demodulating andchannel-decoding the OFDM symbol received through the radio channel andtransmitting the demodulated and channel-decoded OFDM symbol to thehigher layer.

Although not illustrated, RRC layers are present at an upper part of thePDCP layer of the terminal and the base station, and the RRC layer mayreceive and transmit connection and measurement related control messagesfor a RRC.

FIG. 3E is a diagram of a light connection concept, in accordance withan embodiment of the present disclosure.

In FIG. 3E, the light connection technology defines a new terminal modein addition to the idle mode or the connected mode in order to reducethe signaling overhead due to the existing HO and paging transmissionoperation. The new terminal mode can be established as a light connectedmode, an RRC Inactive mode or any other named modes. Hereinafter, forthe terminal 3 e-03 in the light connected mode, the UE context of theterminal is stored, the S1 connection is maintained, and the paging istriggered by the base station 3 e-02 and 3 e-04 or the MME. Therefore,since the terminal 3 e-03 is recognized as the connected mode, if thereis data to be transmitted to the terminal 3 e-03, the MME 3 e-01 doesnot first trigger the paging but immediately transmits the data to thebase station. The base station 3 e-02 and 3 e-04 receiving the dataforwards the paging to all base stations in a predetermined PA 3 e-05,and all base stations transmit the paging.

The terminal 3 e-03 and the network can reduce the battery consumptionand signaling overhead of the terminal 3 e-03 in consideration of theabove-mentioned light connection features.

FIG. 3F is a diagram of a method for establishing a connection of ageneral terminal to a network so that the general terminaltransmits/receives data, in accordance with an embodiment of the presentdisclosure.

When a UE (idle mode UE) 3 f-01 that is not currently connectedgenerates data to be transmitted, the UE 3 f-01 performs anRRCConnectionSetup procedure with the base station 3 f-02. The UE 3 f-01establishes uplink transmission synchronization with the base station 3f-02 through a RAP and transmits an RRCConnectionRequest message to thebase station (at step 3 f-05). The message includes establishmentCauseof connection with the identifier of the UE 3 f-01. The base station 3f-02 transmits an RRCConnectionSetup message to allow the UE 3 f-01 toset the RRC connection (at step 3 f-10). The RRCConnectionSetup messageincludes the RRC connection configuration information, etc. The RRCconnection is also called a SRB and is used for transmission andreception of the RRC message that is a control message between the UE 3f-01 and the base station 3 f-02. The UE 3 f-01 establishing the RRCconnection transmits an RRCConnetionSetupComplete message to the basestation 3 f-02 (at step 3 f-15). The message includes a control messagecalled a service request that that allows the UE 3 f-01 to request abearer setup for a predetermined service to an MME 3 f-03. The basestation 3 f-02 transmits a service request message included in theRRCConnectionSetupComplete message to the MME 3 f-03 (at step 3 f-20)and the MME 3 f-03 determines whether to provide the service the UE 3f-01 requests as the determination result, if the MME 3 f-03 decides toprovide the service that the UE 3 f-01 requests, the MME 3 f-03transmits an initial context setup request message to the base station 3f-02 (at step 3 f-25). The initial context setup request message mayinclude information such as QoS information to be applied when settingup a DRB and security related information (e.g., security key, securityalgorithm) to be applied to the DRB. The base station 3 f-02 exchanges aSecurityModeCommand message at step 3 f-30 and a SecurityModeCompletemessage at step 3 f-35 with the UE 3 f-01 to establish security. Whenthe security establishment is completed, the base station 3 f-02transmits an RRCConnectionReconfiguration message to the UE 3 f-01 (atstep 3 f-40). The message includes the configuration information of theDRB in which user data are processed, and the UE 3 f-01 applies theinformation to setup the DRB and transmits anRRCConnectionReconfigurationComplete message to the base station (atstep 3 f-45). The base station 3 f-02 that completes the DRB setup withthe UE 3 f-01 transmits an initial context setup complete message to theMME 3 f-03 (at step 3 f-50) and the MME 3 f-03 receiving the messageexchanges an S1 bearer setup message and an S1 bearer setup responsemessage with a S-GW 3 f-04 to setup an S1 bearer (at steps 3 f-55 and 3f-60). The S1 bearer is a data transmission connection establishedbetween the S-GW 3 f-04 and the base station 3 f-02 and corresponds to aDRB on a one-to-one basis. If all of the procedures are completed, theUE 3 f-01 transmits and receives data to and from the base station 3f-02 through the S-GW 3 f-04 (at steps 3 f-65 and 3 f-70). As describedabove, the normal data transmission procedure largely consists of threestages: RRCConnectionSetup, security setup, and DRB setup.

FIG. 3G is a diagram of a method of updating, by a general terminal, atracking region, in accordance with an embodiment of the presentdisclosure.

In FIG. 3G, a UE 3 g-01 may establish a tracking area for apredetermined reason (at step 3 g-05). The tracking area may beindicated by a list of tracking area identifiers (IDs). Thepredetermined reason can be established in a procedure in which theterminal initially accesses the network, can be established when thetracking area is periodically updated, and can be established by othercauses. The UE 3 g-01 may establish the tracking area by receiving atracking area update (TAU) accept message by an MME in the tracking areaestablishing procedure. The TAU accept message may be included in theRRC message, and may be transmitted to the terminal by being includedin, for example, the DedicatedInfoNAS of theRRCConnectionReconfiguration message or DLInformationTransfer message.The base station (old eNB) 3 g-03 may disconnect the UE 3 g-01 for apredetermined reason (at step 3 g-10). The predetermined reason may bethat the inactive timer expires because there is no datatransmission/reception between the UE 3 g-01 and the network for apredetermined time. The UE 3 g-01 returns to the idle mode and can moveaccording to the movement of the user. The UE 3 g-01 may out of theestablished tracking area due to the mobility (at step 3 g-15), confirmthe tracking area identifier from the system information of the currentcell (at step 3 g-20), and perform the TAU procedure (at step 3 g-30).The UE 3 g-01 may transmit the RRCConnectionRequest message to the basestation 3 g-03 in order to establish a connection to the new basestation or the cell 3 g-02 and to update the tracking area at step 3g-35. The RRC message may try to update the tracking area by mo (mobileoriginated)-signaling the RRC connection establishmentCause. The basestation 3 g-02 can send the RRCConnectionSetup message to the UE 3 g-01to allow the RRCConnectionSetup (at step 3 g-40). In order to update thetracking area setup, the UE 3 g-01 may transmit the TAU request messageby including the TAU request message in the DedicatedInfoNAS of theRRCConnectionSetupComplete message (at step 3 g-45). The base station 3g-02 may transmit the TAU request message to an MME 3 g-04 to requestthe TAU (at step 3 g-50). When receiving the TAU request message andaccepting the TAU, the MME 3 g-04 transmits the TAU accept message tothe base station 3 g-02 (at step 3 g-55), and the base station 3 g-02transmits the TAU accept message to the UE 3 g-01 by including the TAUaccept message in the RRC message. The TAU accept message may includenew tracking area information. The RRC message transmitted from the basestation 3 g-02 to the UE 3 g-01 may be an RRCConnectionReconfigurationmessage or a DLInformationTransfer message.

FIG. 3H is a diagram of a method of a terminal and a base station forsupporting a light connection in a next generation mobile communicationsystem, in accordance with an embodiment of the present disclosure.

FIG. 3H illustrates the overall flow of a terminal (UE) 3 h-01, ananchor eNB (base station) 3 h-02, a new eNB 3 h-03, and an MME 3 h-04 sothat the terminal 3 h-01 and the base station 3 h-02 performs the UEcontext (terminal context) and the SI bearer. The terminal 3 h-01 in theRRC connected state performs data transmission/reception with the basestation 3 h-02. When the data transmission/reception stops, the basestation 3 h-02 drives a predetermined timer and if the datatransmission/reception is not resumed until the timer expires (at step 3h-05), the base station 3 h-02 considers releasing the RRC connection ofthe terminal 3 h-01. The base station 3 h-02 may release the RRCconnection of the terminal 3 h-01 according to a predetermined rule,store the UE context, allocate a Resume ID while transmitting a controlmessage instructing the terminal 3 h-01 to release the RRC connection,and allow the terminal 3 h-01 to establish the paging area (PA) to whichthe mobility is reported during the light connected mode. In this case,it can be appreciated that the terminal 3 h-01 should store the UEcontext due to the Resume ID allocation. Alternatively, the base station3 h-02 may send to the message a separate context retention indicationthat instructs the base station 3 h-02 to operate the terminal 3 h-01 inthe light connected mode and to store the UE context (at step 3 h-10).In addition, the control message may include a list of cells, or thelike to which a procedure of using the stored context may be applied,when the base station 3 h-02 tries to again setup the RRC connectionwithin the period when the UE context is retained or the expiration dateof the UE. The PA may be constructed and configured in the paging areaidentify of the PA or the list of cell identifiers (IDs). The basestation 3 h-02 releases the RRC connection of the terminal 3 h-01 andthen retains the UE context and the S1 bearer of the UE as they are (atstep 3 h-15). The S1 bearer is called an S1-control bearer used totransmit and receive the control message between the base station 3 h-02and an MME 3 h-04 and an S1-user plane bearer used to transmit andreceive user data between the base station 3 h-02 and the S-GW 3 h-04.By retaining the S1 bearer, it is possible to omit the procedure for S1bearer setup when the terminal 3 h-01 tries to setup an RRC connectionin the same cell or in the same base station. If the expiration dateexpires, the base station 3 h-02 may delete the UE context and releasethe S1 bearer. The terminal 3 h-01 receiving the RRC connection releasemessage in step 3 h-10 is switched to the light connected mode.

The base station base station 3 h-02 transmits a control messagerequesting a connection pause to the MME 3 h-04 (at step 3 h-20). TheMME 3 h-04 receiving the control message requests the S-GW to allow theMME 3 h-04 to start the paging procedure without transmitting thedownlink data to the base station when the downlink data for theterminal 3 h-01 is generated, the S-GW is operated accordingly (at step3 h-35) or immediately transmits the downlink data to an anchor eNB 3h-03 when the downlink data for the terminal 3 h-01 is generated, andthe anchor eNB 3 h-03 may generate the paging message and transmit thegenerated paging message to neighboring base stations. That is, theanchor eNB 3 h-03 receiving the downlink data stores the data in thebuffer and performs the paging procedure. The anchor eNB 3 h-03 is namedthe base station 3 h-02 that maintains the UE context and the S1-Ubearer of the terminal.

The terminal 3 h-01 receiving the RRC connection release message at step3 h-10 including the information indicating the context retention andthe resume ID may release the RRC connection, drive the timercorresponding to the expiration date and record a valid cell list in thememory, maintain the currently terminal context in the memory withoutdeleting the currently terminal context (at step 3 h-25) and may beshifted to the light connected mode. In above description, the UEcontext is various information associated with the RRC connection of theterminal 3 h-01 and includes SRB setup information, DRB setupinformation, security key information, etc. Hereinafter, for any reason,a necessity to setup the RRC connection may be generated (at step 3h-30). A terminal that has not been allocated the Resume ID or is notinstructed to maintain the context during the previous RRC connectionrelease initiates the general RRCConnectionSetup process described inFIG. 3F, but the light connected mode terminal which has been allocatedthe Resume ID during the previous RRC connection release may try theRRCConnectionResume process using the stored terminal context.

In above description, the light connected mode terminal may perform thegeneral RRCConnectionSetup process (FIG. 3F) and perform theRRCConnectionResume process using the stored terminal context accordingto whether to support the light connection of the network. In thepresent disclosure, each base station or cell may transmit an indicationas to whether or not each base station or cell supports the lightconnection by including the indication in the system information. Theindication may be included in a second bloc of system information(Systeminformation 2), or may be included in blocks of other systeminformation (Systeminformation 1 to 19). In the above description,supporting the light connection may mean that the corresponding basestation 3 h-02 or the corresponding cell may establish and support thefollowing at steps 3 h-50, 3 h-55, 3 h-60, 3 h-65, 3 h-70, 3 h-75, 3h-80, 3 h-85, and 3 h-90. If the light connected mode terminal needs toestablish the RRC connection, it reads the system information of thecurrently camped-on cell. If the system information does not include theindication that the base station 3 h-02 or the cell supports lightconnection, the terminal 3 h-01 can perform the general RRC connectionestablishment procedure described in FIG. 3F (at step 3 h-45). However,if the system information includes the indication that the base station3 h-02 or the cell supports light connection, the terminal 3 h-02 canperform an RRCConnectionResume process using the stored UE context (atstep 3 h-45). The RRCConnectionResume process using the stored UEcontext is as follows.

First, the terminal 3 h-01 transmits a preamble in a message 1 toperform the RAP. If the resource allocation is possible according to thepreamble received in the message 1, the base station 3 h-02 allocatesthe corresponding uplink resource to the terminal 3 h-01 in q message 2.The terminal 3 h-01 transmits a Resume request message including theResume ID received in step 3 h-10 based on the received uplink resourceinformation (at step 3 h-50). The message may be a modified message ofthe RRCConnectionRequest message or a newly defined message (e.g.,RRCConnectionResumeRequest). When the terminal 3 h-01 in the lightconnected mode moves to camp on the cell of another base station byreleasing the connection from the existing anchor eNB, e.g., basestation 3 h-02, (at step 3 h-02), the new base station 3 h-03 receivesand confirms the Resume ID of the terminal, such that it can beappreciated from which base station the corresponding terminal receivesa service previously. If the new base station 3 h-03 successfullyreceives and confirms the Resume ID, it performs a procedure ofretrieving the UE context from the existing base station 3 h-02 (ContextRetrieve Procedure at steps 3 h-55 and 3 h-60). The new base station 3h-03 may obtain the terminal context from the existing base station 3h-02 through the S1 or X2 interface. If the new base station 3 h-03receives the Resume ID but fails to successfully identify the terminal 3h-01 for predetermined reasons, the RRC connection establishmentprocedure may be sent to the terminal 3 h-01 and may return to thegeneral connection setup procedure described in FIG. 3F. That is, if theRRCConnectionSetup message is sent to the terminal 3 h-01 and theterminal 3 h-01 receives the message, the RRCConnectionSetup message maybe sent to the base station 3 h-02 to establish the connection.Alternatively, if the new base station 3 h-03 receives the Resume ID butdoes not successfully identify the terminal 3 h-01 (e.g., when fails toretrieve the UE context from the existing anchor eNB), theRRCConnectionRelease message or the RRCConnectionReject message is sentto the terminal 3 h-01 to reject the connection of the terminal 3 h-01and the general RRCConnectionSetup procedure described in FIG. 2F may betried from the beginning.

The new base station 3 h-03 confirms the MAC-I based on the retrieved UEcontext (at step 3 h-65). The MAC-I is a message authentication codecalculated by the terminal 3 h-01 for the control message by applyingthe security information of the restored UE context, that is, applying asecurity key and a security counter. The base station 3 h-03 confirmsthe integrity of the message using the MAC-I of the message, a securitykey, a security counter stored in the context of the terminal 3 h-01, orthe like. The base station 3 h-03 determines the establishment to beapplied to the RRC connection of the terminal 3 h-01 and transmits theRRCConnectionResume receiving the configuration information to theterminal 3 h-01 (at step 3 h-70). The RRCConnectionResume message may bea control message in which the reuse indicator indicating ‘RRC contextreuse’ is included in the general RRC connection request message. TheRRCConnectionResume message modified RRCConnectionSetup message receivesvarious information related to the RRCConnectionSetup of the terminallike the RRCConnectionSetup message. When the terminal 3 h-01 receivesthe normal RRCConnectionSetup message, the terminal 3 h-01 establishesthe RRC connection on the basis of the configuration informationindicated in the RRC connection setup message, but when the terminal 3h-01 receives the RRCConnectionResume message, the terminal 3 h-01establishes (delta configuration) the RRC connection in consideration ofboth of the stored configuration information and the configurationinformation indicated in the control message.

In summary, the terminal 3 h-01 determines the indicated configurationinformation as the delta information on the stored configurationinformation to determine the configuration information to be applied andupdates the configuration information or the UE context. For example, ifthe modified RRCConnectionResume message includes the SRB configurationinformation, the SRB is configured by applying the indicated SRBconfiguration information, and if the SRB configuration information isnot included in the RRCConnectionResume message, the SRB may beconfigured by applying the SRB configuration information stored in theUE context.

The terminal 3 h-01 configures the RRC connection by applying theupdated terminal and the configuration information and transmits theRRCConnectionResumeComplete message to the base station 3 h-03 (at step3 h-75). The control message requesting the connection pause to the MME3 h-04 is transmitted and the S1 bearer is requested to be reestablishedin a new base station (3 h-80 and 3 h-85). When receiving the message,the MME instructs the S-GW to reestablish the S1 bearer as a new basestation and normally process data for the terminal 3 h-01. When theprocess is completed, the terminal resumes data transmission/receptionin the cell (at step 3 h-90).

In the above procedure, if the terminal 3 h-01 in the light connectedmode does not greatly move by releasing the connection from the basestation (anchor eNB) 3 h-02, and thus if the camped-on cell (basestation 3 h-02) of the existing anchor eNB 3 h-03 is made, the existinganchor eNB 3 h-03 does not perform steps 3 h-55 and 3 h-60 but performsonly the connection pause of the S1 bearer in place of steps 3 h-80 and3 h-85 and refers to the Resume ID indicated in the message 3 to searchfor the UE context of the terminal and reestablish the connection by themethod similar to the above procedures based on the same.

If the data transmission/reception stops, the base station 3 h-02 drivesa predetermined timer and if the data transmission/reception is notresumed until the timer expires (at step 3 h-95), the base station 3h-02 considers releasing the RRC connection of the terminal 3 h-02. Thebase station 3 h-02 may release the RRC connection of the terminal 3h-01 according to a predetermined rule, store the UE context, allocate aResume ID while transmitting a control message instructing the terminal3 h-01 to release the RRC connection, and allow the terminal 3 h-01 toestablish the PA to which the mobility is reported during the lightconnected mode (at step 3 h-100). The terminal 3 h-01 at step 3 h-105 inthe light connected mode performs a procedure of updating the pagingarea if the terminal 3 h-01 at step 3 h-105 is out of the establishedPA.

FIG. 3I is a diagram of a method for performing a paging area update(PAU) to a new base station by the light connected terminal, inaccordance with an embodiment of the present disclosure.

In FIG. 3I, the terminal (UE) 3 i-01 in the connection state with theanchor eNB 3 i-03 receives the RRCConnectionRelease message from theanchor eNB 3 i-03 (at step 3 i-05). If there is no datatransmission/reception for a predetermined period of time, the anchoreNB 3 i-03 can transmit the RRCConnectionRelease message to the terminal3 i-01 to be established in the light connected mode. The RRC messagemay include the information on the resume ID and the PA for thelight-connected terminal 3 i-01. The information on the PA may indicateone or more PA identifiers (PA IDs) or a list of one or more cellidentifiers (Cell IDs). The terminal 3 i-01 receiving the RRC message 3i-03 3 i-05 can go to the light connected mode or the RRC idle state.The anchor eNB 3 i-03 may store the context information of the terminal3 i-01 and may maintain the S1 bearer (at steps 3 i-10 and 3 i-15). Inaddition, the anchor eNB 3 i-03 can manage the mobility of the terminal3 i-01 instead of an MME 3 i-04. That is, if the anchor eNB 3 i-03 hasthe downlink data to be transmitted to the terminal, it can generate apaging message and send the generated paging message to the terminal 3i-01 through the PA.

The terminal 3 i-01 may move to another new base station or cell (neweNB) 3 i-02 in another PA (at step 3 i-20). Each cell managed by thebase stations uses the predetermined system information (SIB) tobroadcast the PA information such as its own cell ID or a PA ID orwhether the cell (base station) supports the light connection (forexample, using the indication) (at step 3 i-25). In step 3 i-30, theterminal 3 i-01 receives the system information of the camped-on celland confirms whether the PA information or the cell supports lightconnection (at step 3 i-30). When the indication indicating that thecell (or the base station) supports light connection is not included inthe system information, the terminal 3 i-01 may perform the general TAUprocedure as shown in FIG. 3G. However, if the indication indicatingthat the cell (or the base station) supports light connection isincluded in the system information, the terminal 3 i-01 can perform themethod of FIG. 3I of updating the following paging area (at step 3i-35).

If the PA ID or the cell identifiers broadcast in the system informationare not included in the PA information established the terminal in step3 i-05, it is determined that the terminal 3 i-01 is out of the PA, andthe RRCConnectionResumeRequest is transmitted to the base station 3 i-02of the currently camped-on cell to request the paging area update (atstep 3 i-40). The establishment cause for the PA updating request in themessage is newly defined and may be included. Alternatively, it mayinclude the indication to indicate that the request is for updating thepaging area using the reserved 1 bit of the message. Also, the messageincludes at least one of the Resume ID, the MAC-I, and the establishmentcause. The base station 3 i-02 receiving the RRCConnectionResumeRequestmessage uses the Resume ID to know the anchor eNB 3 i-03 that previouslysupports the terminal (at step 3 i-45). Accordingly, the base station 3i-02 can request the context information of the terminal 3 i-01 to theanchor eNB 3 i-03 (at steps 3 i-50 and 3 i-55). The securityestablishment can be confirmed using the retrieved terminal contextinformation. The above steps at 3 i-50 and 3 i-55 may be omitted if theterminal 3 i-01 attempts the connection establishment to original anchoreNB 3 i-03. The base station 3 i-02 transmits an RRCConnectionResumemessage to the terminal 3 i-01 in step to allow the terminal 3 i-01 toestablish the connection (at step 3 i-60), and the terminal 3 i-01 cantransmit an RRCConnectionResumeComplete message to complete theconnection setup (at step 3 i-65). In the message, the terminal 3 i-01may transmit a message or an indicator for requesting paging area updateto the base station 3 i-02. The base station 3 i-02 receiving the pagingarea update request can send a paging area update response in the RRCmessage and establish new PA information (at step 3 i-70).

In the above description, the RRC message may be the RRConnectionReleasemessage or the RRCConnectionReconfiguration message and may be a newlydefined RRC message. The base station 3 i-02 can confirm the mobility,speed, traffic pattern, and the like of the terminal 3 i-01 through thehistory information of the terminal 3 i-01, and can establish a new PAof the terminal 3 i-01 by reflecting the information (at step 3 i-70).The history information may be received when a new base stationexchanges messages with the anchor eNB 3 i-03, and may includeinformation such as the number of times, the period, and the time thatthe terminal performs the paging update at steps 3 i-50, 3 i-55. Afterthe base station 3 i-02 updates the PA of the terminal 3 i-01, itupdates the PA for the terminal 3 i-01 of the anchor eNB 3 i-03 (at step3 i-75). Since the anchor eNB 3 i-03 is the base station that maintainsthe terminal context and the SI-U bearer of the terminal 3 i-01 and thebase station that manages the mobility of the terminal 3 i-01, thepaging area of the terminal should be updated. If the downlink data forthe corresponding terminal reaches the anchor eNB 3 i-03 in future, theanchor eNB 3 i-03 managing the mobility of the terminal 3 i-01appropriately generates and transmits the paging message to each findthe terminal 3 i-01.

In the above procedure, if the mobility of the terminal 3 i-01 is smalland the connection to the base station 3 i-03 that is connectedpreviously is attempted, steps 3 i-50, 3 i-55, and 3 i-75 are notperformed and the procedure of updating the PA may be performed.

FIG. 3J is a diagram of a method for performing a PAU to a new basestation by the light connected terminal, in accordance with anembodiment of the present disclosure.

In FIG. 3J, the terminal 3 j-01 in the connection state with the anchoreNB 3 j-03 receives the RRCConnectionRelease message from the anchor eNB3 j-03 (at step 3 j-05). If there is no data transmission/reception fora predetermined period of time, the anchor eNB 3 j-03 can transmit theRRCConnectionRelease message to the terminal 3 j-01 to be established inthe light connected mode. The RRC message may include the information onthe resume ID and the PA for the light-connected terminal. Theinformation on the PA may indicate one or more PA IDs or a list of oneor more Cell IDs. The terminal 3 j-01 receiving the RRC message at step3 j-05 can go to the light connected mode or the RRC idle state. Theanchor eNB 3 j-03 may store the context information of the terminal 3j-01 and may maintain the S1 bearer (at steps 3 j-10 and 3 j-15). Inaddition, the anchor eNB 3 j-03 can manage the mobility of the terminal3 j-01 instead of N MME 3 j-04. That is, if the anchor eNB 3 j-03 hasthe downlink data to be transmitted to the terminal 3 j-01, it cangenerate a paging message and send the generated paging message to themobile station through the PA.

The terminal 3 j-01 may move to another new base station or cell (eNB) 3j-02 in another PA (at step 3 j-20). Each cell managed by the basestations uses the predetermined SIB to broadcast the PA information suchas its own cell ID or a PA ID or whether the cell (base station)supports the light connection (for example, using the indication) (atstep 3 j-25). In step 3 j-30, the terminal 3 j-01 receives the systeminformation of the camped-on cell and confirms whether the PAinformation or the cell supports light connection (at step 3 j-30). Whenthe indication indicating that the cell (or the base station) supportslight connection is not included in the system information, the terminal3 j-01 may perform the general TAU procedure as shown in FIG. 3G.However, if the indication indicating that the cell (or the basestation) supports light connection is included in the systeminformation, the terminal 3 j-01 can perform the method of FIG. 3J forupdating the following PA (at step 3 j-35).

If the PA ID or the cell identifiers broadcast in the system informationare not included in the PA information established the terminal 3 j-01in step 3 j-05, it is determined that the terminal 3 j-01 is out of thePA, and the RRCConnectionResumeRequest is transmitted to the basestation of the currently camped-on cell to request the PA update (atstep 3 j-40). The establishment cause for the paging area updatingrequest in the message is newly defined and may be included.Alternatively, it may include the indication to indicate that therequest is for updating the paging area using the reserved 1 bit of themessage. Also, the message includes at least one of the Resume ID, theMAC-I, and the establishment cause. The base station receiving theRRCConnectionResumeRequest message uses the Resume ID to know the anchoreNB 3 j-03 that previously supports the terminal 3 j-01 (at step 3j-45). Accordingly, the new base station 3 j-02 can request the contextinformation of the terminal 3 j-01 to the anchor eNB 3 j-03 (at steps 3j-50 and 3 j-55). The security establishment can be confirmed using theretrieved terminal context information. The above steps 3 j-50 and 3j-55 may be omitted if the terminal 3 j-01 attempts the connectionestablishment to original anchor eNB 3 j-03. The base station 3 j-02 cantransmit a RRCConnectionResume message at step 3 j-60 in order toreceive the PA update request of the terminal 3 j-01 in the message atstep 3 j-40 and permit the PA update message (at step 3 j-60). The basestation 3 j-02 may include information on a new PA in response to thepaging area update request in the message, and may include a new resumeID, and if necessary, the new resume ID may be transmitted to theterminal 3 j-01 by being included in the RRCConnectionRelease message atstep 3 j-75.

The new base station 3 j-02 can confirm the mobility, speed, trafficpattern, and the like of the terminal 3 j-01 through the historyinformation of the terminal 3 j-01, and can establish a new paging areaof the terminal 3 j-01 by reflecting the information (3 j-70). Thehistory information may be received when a new base station 3 j-02exchanges messages with the anchor eNB 3 j-03, and may includeinformation such as the number of times, the period, and the time thatthe terminal 3 j-01 performs the paging update procedure (3 i-50, 55).After the new base station 3 j-02 updates the paging area of theterminal 3 j-01, it updates the paging area for the terminal of theanchor eNB 3 j-03 (at step 3 j-65). The terminal 3 j-01 can transmit theRRCConnectionResumeComplete message to complete the connectionestablishment (at step 3 j-70). If there is no datatransmission/reception while the predetermined time elapses, the basestation 3 j-02 can send the RRCConnectionRelease message to establishthe terminal 3 j-01 to be in the light connected mode again (at step 3j-75). Since the anchor eNB 3 j-03 is the base station 3 j-01 thatmaintains the terminal 3 j-01 context and the SI-U bearer of theterminal 3 j-01 and the base station 3 j-02 that manages the mobility ofthe terminal 3 j-01, the paging area of the terminal 3 j-01 should beupdated. If the downlink data for the corresponding terminal 3 j-01reaches the anchor eNB 3 j-03 in future, the anchor eNB 3 j-03 managingthe mobility of the terminal appropriately generates and transmits thepaging message to each find the terminal 3 j-01.

In the above procedure, if the mobility of the terminal 3 j-01 is smalland the connection to the base station 3 j-03 that is connectedpreviously is attempted, steps 3 j-50, 3 j-55, and 3 j-65 are notperformed and the method of FIG. 3J for updating the PA may beperformed.

FIG. 3K is a diagram of a method for performing a PAU to a new basestation by the light connected terminal, in accordance with anembodiment of the present disclosure.

In FIG. 3K, the terminal 3 k-01 in the connection state with the anchoreNB 3 k-03 receives the RRCConnectionRelease message from the anchor eNB(at step 3 k-05). If there is no data transmission/reception for apredetermined period of time, the anchor eNB 3 k-03 can transmit theRRCConnectionRelease message to the terminal 3 k-01 to be established inthe light connected mode. The RRC message may include the information onthe resume ID and the PA for the light-connected terminal. Theinformation on the PA may indicate one or more PA IDs or a list of oneor more Cell IDs. The terminal 3 k-01 receiving the RRC message at step3 k-05 can go to the light connected mode or the RRC idle state. Theanchor eNB 3 k-03 may store the context information of the terminal 3k-01 and may maintain the S1 bearer (at steps 3 k-10 and 3 k-15). Inaddition, the anchor eNB 3 k-03 can manage the mobility of the terminal3 k-01 instead of an MME 3 k-04. That is, if the anchor eNB 3 k-03 hasthe downlink data to be transmitted to the terminal 3 k-01, it cangenerate a paging message and send the generated paging message to themobile station through the PA.

The terminal 3 k-01 may move to another new base station or cell 3 k-02in another PA (at step 3 k-20). Each cell managed by the base stationsuses the predetermined SIB to broadcast the PA information such as itsown cell ID or a PA ID or whether the cell (base station) supports thelight connection (for example, using the indication) (at step 3 k-25).In step 3 k-30, the terminal 3 k-01 receives the system information ofthe camped-on cell and confirms whether the PA information or the cellsupports light connection (at step 3 k-30). When the indicationindicating that the cell (or the base station) supports light connectionis not included in the system information, the terminal 3 k-01 mayperform the general TAU procedure as shown in FIG. 3G. However, if theindication indicating that the cell (or the base station) supports lightconnection is included in the system information, the terminal 3 k-01can perform the method of FIG. 3K for updating the PA (at step 3 k-35).

If the PA ID or the cell identifiers broadcast in the system informationare not included in the paging area information established the terminalin step 3 k-05, it is determined that the terminal is out of the PA, andthe RRCConnectionResumeRequest is transmitted to the base station of thecurrently camped-on cell to request the paging area update (at step 3k-40). The establishment cause for the PA updating request in themessage is newly defined and may be included. Alternatively, it mayinclude the indication to indicate that the request is for updating thePA using the reserved 1 bit of the message. Also, the message includesat least one of the Resume ID, the MAC-I, and the establishment cause.The base station receiving the RRCConnectionResumeRequest message usesthe Resume ID to know the anchor eNB 3 k-03 that previously supports theterminal 3 k-01 (at step 3 k-45). Accordingly, the new base station 3k-02 can request the context information of the terminal 3 k-01 to theanchor eNB 3 k-03 (at steps 3 k-50 and 3 k-55). The securityestablishment can be confirmed using the retrieved terminal contextinformation. The steps of 3 k-50 and 3 k-55 may be omitted if theterminal 3 k-01 attempts the connection establishment to original anchoreNB 3 k-03. The base station 3 k-02 can transmit the RRC message as theresponse to the PA update request in order to receive the PA updaterequest of the terminal 3 k-01 in the message at step 3 k-40 and permitthe PA update message (at step 3 k-60). The base station 3 k-02 mayinclude information on a new PA as response to the paging area updaterequest in the message, and may include a new resume ID. The RRC messagemay be a newly defined RRC message, an RRCConnectionRelease message, anRRCConnectionReconfiguration message, or an RRCConnectionResume message.The new base station 3 k-02 can confirm the mobility, speed, trafficpattern, and the like of the terminal 3 k-01 through the historyinformation of the terminal, and can establish a new PA of the terminal3 k-01 by reflecting the information (at step 3 k-60). The historyinformation may be received when a new base station 3 k-02 exchangesmessages with the anchor eNB 3 k-03, and may include information such asthe number of times, the period, and the time that the terminal performsthe paging update procedure (at step 3 k-50, 3 k-55). After the new basestation 3 k-02 updates the PA of the terminal 3 k-01, it updates thepaging area for the terminal 3 k-01 of the anchor eNB 3 k-03 (at step 3k-65). If there is no data transmission/reception while thepredetermined time elapses, the base station 3 k-02 may send theRRCConnectionRelease message and again establish the terminal in thelight connected mode or may omit the message when using theRRCConnectionRelease message in step 3 k-60. Since the anchor eNB 3 k-03is the base station 3 k-03 that maintains the terminal context and theSI-U bearer of the terminal 3 k-01 and the base station 3 k-02 thatmanages the mobility of the terminal 3 k-01, the PA of the terminal 3k-01 should be updated. If the downlink data for the correspondingterminal 3 k-01 reaches the anchor eNB 3 k-03 in future, the anchor eNB3 k-03 managing the mobility of the terminal 3 k-01 appropriatelygenerates and transmits the paging message to each find the terminal.

In the above procedure, if the mobility of the terminal 3 k-01 is smalland the connection to the base station (eNB) 3 k-03 that is connectedpreviously is attempted, steps 3 k-50, 3 k-55, 3 k-65 are not performedand the method of FIG. 3K for updating the PA may be performed.

FIG. 3I is a flowchart of a method of a terminal when the lightconnected mode terminal establishes an RRC connection to the network, inaccordance with an embodiment of the present disclosure.

In FIG. 31, the terminal in the connection state to the anchor eNBreceives an RRC ConnectionRelease message from the anchor eNB (at step 3l-05). The anchor eNB may establish the terminal in the light connectedmode if there is no data transmission/reception for the predeterminedtime. The terminal receiving the message is switched to the lightconnected mode (at step 3 l-10). Also, the terminal receiving theRRCConnectionRelease message may go to the RRC idle state. The terminalis allocated the Resume ID through the RRCConnectionRelease message andestablishes the PA information. In the above description, the PA mayindicate one or more than two sets of cells, and may indicate one or twoor more PA ID (at step 3 l-05). The terminal may move to another PA ofthe existing anchor eNB or another base station. If it is necessary forthe terminal to establish the RRCConnectionsetup to the network for apredetermined reason, the terminal performs a cell reselection procedureand searches for a suitable cell (at step 3 l-15). If an appropriatecell is found in the cell reselection procedure, the cell is camped onand the system information is read (at step 3 l-20). The terminalconfirms whether the PA information or the camped-on cell in the systeminformation supports light connection (at step 3 l-25). If the cell doesnot support the light connection, the terminal performs the general RRCconnection establishment procedure described in FIG. 3F (at step 3l-30). If the cell supports light connection, the terminal performs theRRCConnectionResume procedure based on the terminal context as describedin FIG. 3H (at step 3 l-35).

FIG. 3M is a flowchart of a method of the terminal when the lightconnected mode terminal performs the procedure of performing the pagingarea update, in accordance with an embodiment of the present disclosure.

In FIG. 3M, the terminal in the connection state to the anchor eNBreceives an RRCConnectionRelease message from the anchor eNB (at step 3m-05). The anchor eNB may establish the terminal in the light connectedmode if there is no data transmission/reception for the predeterminedtime. The terminal receiving the message is switched to the lightconnected mode (at step 3 m-10). Also, the terminal receiving theRRCConnectionRelease message may go to the RRC idle state. The terminalis allocated the Resume ID through the RRCConnectionRelease message andestablishes the PA information. In the above description, the PA mayindicate one or more than two lists of cells, and may indicate one ortwo or more PA (at step 3 m-05). The terminal may move to another PA ofthe existing anchor eNB or another base station. The terminal performs acell reselection procedure to search for a suitable cell (at step 3m-15). If an appropriate cell is found in the cell reselectionprocedure, the cell is camped on and the system information is read (atstep 3 m-20). The terminal confirms the PA information in the systeminformation, compares the confirmed PA information with the PAinformation established in step 3 m-05, and then determines the PA as adifferent paging area if the terminal does not have the same PAinformation (at step 3 m-25). If the PA information read from the systeminformation is included in the PA information established in step 3m-05, the terminal determines that it is within the established pagingarea and continuously performs the cell reselection procedure withoutperforming the PA update procedure (at step 3 m-15). If it is determinedthat the terminal is currently in another PA, the process proceeds tostep 3 m-30 to check whether the currently camped-on cell supports thelight connection in the system information. If the currently camped-oncell does not support the light connection, the terminal performs thegeneral TAU procedure described in FIG. 3G (at step 3 m-35), and if thecurrently camped-on cell supports the light conception, the methodsdescribed in FIGS. 3I, 3J, and 3K is performed (at step 3 m-40).

FIG. 3N is a diagram of the terminal, in accordance with an embodimentof the present disclosure.

The terminal includes an RF processor 3 n-10, a baseband processor 3n-20, a memory 3 n-30, and a controller 3 n-40 including a multipleconnection processor 3 n-42.

The RF processor 3 n-10 serves to transmit and receive a signal througha radio channel, such as band conversion and amplification of a signal.That is, the RF processor 3 n-10 up-converts a baseband signal providedfrom the baseband processor 3 n-20 into an RF band signal and thentransmits the RF band signal through an antenna and down-converts the RFband signal received through the antenna into the baseband signal. TheRF processor 3 n-10 may include a transmitting filter, a receivingfilter, an amplifier, a mixer, an oscillator, a DAC, an ADC, or thelike. FIG. 3N illustrates only one antenna but the terminal may includea plurality of antennas. The RF processor 3 n-10 may include a pluralityof RF chains. Further, the RF processor 3 n-10 may perform beamforming.The RF processor 3 n-10 may adjust a phase and a size of each of thesignals transmitted and received through a plurality of antennas orantenna elements. In addition, the RF processor 3 n-10 may perform MIMOand may receive a plurality of layers when performing a MIMO operation.The RF processor 3 n-10 may perform reception beam sweeping byappropriately configuring a plurality of antennas or antenna elementsunder the control of the controller or adjust a direction and a beamwidth of the reception beam so that the reception beam is resonated withthe transmission beam.

The baseband processor 3 n-20 performs a conversion function between abaseband signal and a bit string according to a physical layer standardof a system. When data are transmitted, the baseband processor 3 n-20generates complex symbols by coding and modulating a transmitted bitstring. When data is received, the baseband processor 3 n-20 recoversthe received bit string by demodulating and decoding the baseband signalprovided from the RF processor 3 n-10. For example, according to theOFDM scheme, when data is transmitted, the baseband processor 3 n-20generates the complex symbols by coding and modulating the transmittingbit string, maps the complex symbols to sub-carriers, and then performsan IFFT operation and a CP insertion to construct the OFDM symbols. Whendata are received, the baseband processor 3 n-20 divides the basebandsignal provided from the RF processor 3 n-10 in an OFDM symbol unit andrecovers the signals mapped to the sub-carriers by an FFT operation andthen recovers the received bit string by the modulation and decoding.

The baseband processor 3 n-20 and the RF processor 3 n-10 transmit andreceive a signal as described above. Therefore, the baseband processor 3n-20 and the RF processor 3 n-10 may be called a transmitter, areceiver, a transceiver, or a communication unit. At least one of thebaseband processor 3 n-20 and the RF processor 3 n-10 may include aplurality of communication modules to support a plurality of differentRATs. At least one of the baseband processor 3 n-20 and the RF processor3 n-10 may include different communication modules to process signals indifferent frequency bands. The different wireless access technologiesmay include an LTE network, an NR network, and the like. Further,different frequency bands may include an SHF (for example: 2.5 GHz, 5GHz) band, a millimeter wave (for example: 60 GHz) band.

The memory 3 n-30 stores data such as basic programs, applicationprograms, and configuration information for the terminal. Further, thememory 3 n-30 provides the stored data according to the request of thecontroller 3 n-40.

The controller 3 n-40 controls the overall operations of the terminal.The controller 3 n-40 transmits and receives a signal through thebaseband processor 3 n-20 and the RF processor 3 n-10. The controller 3n-40 records and reads data in and from the memory 3 n-40. Thecontroller 3 n-40 may include at least one processor, and may include aCP performing a control for communication and an AP controlling a higherlayer such as the application programs.

FIG. 3O is a diagram of TRP in a wireless communication system,according to an embodiment of the present disclosure.

As illustrated in FIG. 3O, the base station is configured to include anRF processor 3 o-10, a baseband processor 3 o-20, a communication unit 3o-30, a memory 3 o-40, and a controller 3 o-50.

The RF processor 3 o-10 serves to transmit and receive a signal througha radio channel, such as band conversion and amplification of a signal.That is, the RF processor 3 o-10 up-converts a baseband signal providedfrom the baseband processor 3 o-20 into an RF band signal and thentransmits the RF band signal through an antenna and down-converts the RFband signal received through the antenna into the baseband signal. TheRF processor 3 o-10 may include a transmitting filter, a receivingfilter, an amplifier, a mixer, an oscillator, a DAC, an ADC, or thelike. FIG. 3O illustrates only one antenna but the first access node mayinclude a plurality of antennas. The RF processor 3 o-10 may include aplurality of RF chains. Further, the RF processor 3 o-10 may perform thebeamforming. The RF processor 3 o-10 may adjust a phase and a size ofeach of the signals transmitted/received through a plurality of antennasor antenna elements. The RF processor 3 o-10 may perform a downward MIMOoperation by transmitting one or more layers.

The baseband processor 3 o-20 performs a conversion function between thebaseband signal and the bit string according to the physical layerstandard of the first RAT. When data are transmitted, the basebandprocessor 3 o-20 generates complex symbols by coding and modulating atransmitted bit string. When data are received, the baseband processor 3o-20 recovers the received bit string by demodulating and decoding thebaseband signal provided from the RF processor 3 o-10. For example,according to the OFDM scheme, when data are transmitted, the basebandprocessor 3 o-20 generates the complex symbols by coding and modulatingthe transmitting bit string, maps the complex symbols to thesub-carriers, and then performs the IFFT operation and the CP insertionto construct the OFDM symbols. When data are received, the basebandprocessor 3 o-20 divides the baseband signal provided from the RFprocessor 3 o-10 in the OFDM symbol unit and recovers the signals mappedto the sub-carriers by the FFT operation and then recovers the receivingbit string by the modulation and decoding. The baseband processor 3 o-20and the RF processor 3 o-10 transmit and receive a signal as describedabove. Therefore, the baseband processor 3 o-20 and the RF processor 3o-10 may be called a transmitter, a receiver, a transceiver, or acommunication unit.

The communication unit 3 o-30 provides an interface for performingcommunication with other nodes within the network.

The memory 3 o-40 stores data such as basic programs, applicationprograms, and setting information for the main base station. Inparticular, the memory 3 o-40 may store the information on the bearerallocated to the accessed terminal, the measured results reported fromthe accessed terminal, etc. The memory 3 o-40 may store information thatis a determination criterion on whether to provide a multiple connectionto the terminal or stop the multiple connection to the terminal. Thememory 3 o-40 provides the stored data according to the request of thecontroller 3 o-50.

The controller 3 o-50 controls the general operations of the main basestation. The controller 3 o-50 transmits/receives a signal through thebaseband processor 3 o-20 and the RF processor 3 o-10 or thecommunication unit 3 o-30. Further, the controller 3 o-50 records andreads data in and from the memory 3 o-40. For this purpose, thecontroller 3 o-50 may include at least one processor.

FIG. 4A is a diagram of the LTE system, in accordance with an embodimentof the present disclosure.

Referring to FIG. 4A, the wireless communication system is configured toinclude a plurality of base stations 4 a-05, 4 a-10, 4 a-15, and 4 a-20,an MME 4 a-25, an S-GW 4 a-30. UE or terminal 4 a-35 accesses anexternal network through the base stations 4 a-05, 4 a-10, 4 a-15, and 4a-20 and the S-GW 4 a-30.

The base stations 4 a-05, 4 a-10, 4 a-15, and 4 a-20 are access nodes ofa cellular network and provides a wireless access to terminals that areconnected to a network. That is, in order to serve traffic of users, thebase stations 4 a-05, 4 a-10, 4 a-15, and 4 a-20 collect stateinformation such as a buffer state, an available transmission powerstate, a channel state, or the like of the terminals to performscheduling, thereby supporting a connection between the terminals and aCN. The MME 4 a-25 is an apparatus for performing various controlfunctions as well as a mobility management function for the terminal 4a-35 and is connected to the plurality of base stations 4 a-05, 4 a-10,4 a-15, and 4 a-20, and the S-GW 4 a-30 is an apparatus for providing adata bearer. The MME 4 a-25 and the S-GW 4 a-30 may further performauthentication, bearer management, etc., on the terminal 4 a-35connected to the network and may process packets that are to be receivedfrom the base stations 4 a-05, 4 a-10, 4 a-15, and 4 a-20 and packetsthat are to be transmitted to the base stations 4 a-05, 4 a-10, 4 a-15,and 4 a-20.

FIG. 4B is a diagram of a radio protocol structure in an LTE system, inaccordance with an embodiment of the present disclosure.

Referring to FIG. 4B, the radio protocol of the LTE system is configuredto include PDCPs 4 b-05 and 4 b-40, RLCs 4 b-10 and 4 b-35, and MACs 4b-15 and 4 b-30 in the terminal and the eNB, respectively. The PDCPs 4b-05 and 4 b-40 control IP header compression/decompression. The mainfunctions of the PDCP are summarized as follows.

Header compression and decompression function (Header compression anddecompression: ROHC only)

Transfer function of user data (Transfer of user data)

In-sequence delivery function (In-sequence delivery of upper layer PDUsat PDCP re-establishment procedure for RLC AM)

Reordering function (For split bearers in DC (only support for RLC AM):PDCP PDU routing for transmission and PDCP PDU reordering for reception)

Duplicate detection function (Duplicate detection of lower layer SDUs atPDCP re-establishment procedure for RLC AM)

Retransmission function (Retransmission of PDCP SDUs at HO and, forsplit bearers in DC, of PDCP PDUs at PDCP data-recovery procedure, forRLC AM)

Ciphering and deciphering function (Ciphering and deciphering)

Timer-based SDU discard function (Timer-based SDU discard in uplink)

The RLCs 4 b-10 and 4 b-35 reconfigures the PDU to an appropriate sizeto perform the ARQ operation or the like. The main functions of the RLCare summarized as follows.

Data transfer function (Transfer of upper layer PDUs)

ARQ function (Error Correction through ARQ (only for AM data transfer))

Concatenation, segmentation, reassembly functions (Concatenation,segmentation and reassembly of RLC SDUs (only for UM and AM datatransfer))

Re-segmentation function (Re-segmentation of RLC data PDUs (only for AMdata transfer))

Reordering function (Reordering of RLC data PDUs (only for UM and AMdata transfer)

Duplicate detection function (Duplicate detection (only for UM and AMdata transfer))

Error detection function (Protocol error detection (only for AM datatransfer))

RLC SDU discard function (RLC SDU discard (only for UM and AM datatransfer))

RLC re-establishment function (RLC re-establishment)

The MACs 4 b-15 and 4 b-30 are connected to several RLC layer devicesconfigured in one terminal and perform multiplexing RLC PDUs into an MACPDU and demultiplexing the RLC PDUs from the MAC PDU. The main functionsof the MAC are summarized as follows.

Mapping function (Mapping between logical channels and transportchannels)

Multiplexing/demultiplexing function (Multiplexing/demultiplexing of MACSDUs belonging to one or different logical channels into/from TBsdelivered to/from the physical layer on transport channels)

Scheduling information reporting function (Scheduling informationreporting)

HARQ function (Error correction through HARQ)

Priority handling function between Logical channels (Priority handlingbetween logical channels of one UE)

Priority handling function between terminals (Priority handling betweenUEs by means of dynamic scheduling)

MBMS service identification function (MBMS service identification)

Transport format selection function (Transport format selection)

Padding function (Padding)

Physical layers 4 b-20 and 4 b-25 perform channel-coding and modulatinghigher layer data, making the higher layer data as an OFDM symbol andtransmitting them to a radio channel, or demodulating andchannel-decoding the OFDM symbol received through the radio channel andtransmitting the demodulated and channel-decoded OFDM symbol to thehigher layer.

Although not illustrated, RRC layers are present at an upper part of thePDCP layer of the terminal and the base station, and the RRC layer mayreceive and transmit connection and measurement related control messagesfor a RRC.

FIG. 4C is a diagram of a method of performing an HO in the existing LTEsystem, in accordance with an embodiment of the present disclosure.

The terminal (UE) 4 c-01 in the connection mode state reports the cellmeasurement information to a source base station (source eNB) 4 c-02when the periodic or specific event is satisfied (at step 4 c-05). Basedon the measurement information, the source base station 4 c-02determines whether to perform an HO to neighboring cells. The HO is atechnique for changing a source base station providing a service to aterminal in a connection mode to another base station. When the sourcebase station 4 c-02 determines the handover, the source base station 4c-02 sends an HO request message to a new base station, i.e., a targetbase station (target eNB) 4 c-03 that services a service to the terminal4 c-01 to request the HO (at step 4 c-10). If the target base station 4c-03 accepts the HO request, it transmits the HO request ACK message tothe source base station 4 c-02 (at step 4 c-15). The source base 4 c-02station receiving the message transmits an HO command message to theterminal 4 c-01 (at step 4 c-20). The source base station 4 c-02transmits the HO command message to the terminal 4 c-01 using the RRCConnectionReconfiguration message (at step 4 c-20). When the terminal 4c-01 receives the message, it stops transmitting/receiving data to/fromthe source base station 4 c-02 and starts a T304 timer. If the terminal4 c-01 fails to succeed the HO to the target base station 4 c-03 for apredetermined time, the T304 timer returns to the original establishmentof the terminal 4 c-01 and switches to the RRC Idle state. The sourcebase station 4 c-02 transmits a SN status for the uplink/downlink dataand transmits it to the target base station 4 c-03 if there is downlinkdata (at steps 4 c-30, 4 c-35). The terminal 4 c-01 attempts randomaccess to the target base station 4 c-03 indicated by the source basestation 4 c-02 (at step 4 c-40).

The random access is to fit an uplink synchronization simultaneouslywith notifying a target cell that the terminal 4 c-01 moves through theHO. For the random access, the terminal 4 c-01 transmits the preamblecorresponding to the preamble ID received from the source base station 4c-02 or the randomly selected preamble ID to the target base station 4c-03. After a certain number of subframes have passed after the preambleis transmitted, the terminal 4 c-01 monitors whether a random accessresponse (RAR) is transmitted from the target base station 4 c-03. Thetime period in which the monitoring is performed is referred to as anRAR window. If the RAR is received during the specific time (at step 4c-45), the terminal 4 c-01 transmits an HO complete message to thetarget base station 4 c-03 by including the HO compete message in anRRCConnectionReconfigurationComplete message (at step 4 c-50). Asdescribed above, if the RAP from the target base station 4 c-03 issuccessfully completed in the MAC, the terminal 4 c-01 ends the T304timer (at step 4 c-55). The target base station 4 c-03 requests the pathmodification to modify the path of the bearers established in the sourcebase station 4 c-02 (at steps 4 c-60, 4 c-65) and notifies the sourcebase station 4 c-02 that the UE context of the terminal 4 c-01 isdeleted. Accordingly, the terminal 4 c-01 attempts to receive data fromthe RAR window starting time for the target base station 4 c-03, andreceives the RAR and then starts the transmission to the target basestation 4 c-03 while transmitting theRRCConnectionReconfigurationComplete message.

Referring to the HO procedure in the LTE system shown in FIG. 4C, thespecific terminal may not transmit or receive its own data until the HOcomplete message (RRCConnectionReconfigurationComplete) is transmittedsince the HO to the target base station 4 c-03 is completed from thetime when the HO command message (RRCConnectionReconfiguration) isreceived from a source base station 4 c-02. This datatransmission/reception disconnection state causes a certain time delayin transmitting/receiving data by the terminal. In the presentdisclosure, a RACH-less HO method that minimizes the data transmissioninterruption time is considered, and the corresponding terminal isspecified. In the RACH-less HO method, when the terminal 4 c-01 performsthe HO from the source base station 4 c-02 to the target base station 4c-03, the RRCConnectionReconfigurationComplete message is directlytransmitted through the uplink resource previously allocated from thetarget base station 4 c-03 without performing the RAP, therebyestablishing the connection with the target base station 4 c-03. TheRACH-less HO may have various embodiments according to a specificoperation procedure.

FIG. 4D is a diagram of a method for performing a RACH-less HO, inaccordance with an embodiment of the present disclosure.

In FIG. 4D, the source base station 4 d-02 may request to the terminal 4d-01 the UE capability information using a UECapabilityEnquiry message(at step 4 d-05). The terminal 4 d-01 can report whether to supportRACH-less HO for each band or band combination to the source basestation using the UECapabilityInformation message (at step 4 d-10). Ifthe source base station 4 d-02 also supports the RACH-less HO for eachband or band combination, the RACH-less HO may be used. The terminal 4c-01 in the connection mode state reports the cell measurementinformation to the source base station (source eNB) 4 d-02 when theperiodic or specific event is satisfied (at step 4 d-15). Based on themeasurement information, the source base station 4 d-02 determineswhether to perform an HO to neighboring cells. When the source basestation 4 d-02 determines the HO, the source base station 4 d-02 sendsan HO request message to a new base station, i.e., a target base station(target eNB) 4 d-03 that services a service to the terminal 4 d-01 torequest the HO (at step 4 c-20). The source base station 4 d-02additionally determines whether the target base station 4 d-03 appliesRACH-less HO to the terminal 4 d-01 supporting the RACH-less HO, andthen requests HO to the target base station 4 d-03 (at step 4 d-20). Inaddition, when the HO is requested, it may include an indication(Indication 1) indicating whether to apply the RACH-less HO. If thetarget base station 4 d-03 accepts the HO request, it transmits the HOrequest ACK message to the source base station 4 d-02 (at step 4 c-25).The HO request Ack message includes the configuration information of atarget base station 4 d-03 necessary for handover. The configurationinformation may include an indication (indication 2) indicating thatRACH-less HO is supported when the target base station 4 d-03 supportsthe RACH-less HO and the information on an uplink transmission resourcethat can be used when the terminal 4 d-01 sends an RRC message(RRConnectionReconfigurationComplete) to the target base station 4 d-03.The source base station 4 d-02 instructs the terminal 4 d-01 to performthe HO to the target base station 4 d-03 using theRRCConnectionReconfiguration message (at step 4 d-30). At this time, theRRC message includes one indication (indication 2) indicating to performthe RACH-less HO, and the information on an uplink transmission resourcethat can be used when the terminal 4 d-01 sends an RRC message(RRConnectionReconfigurationComplete) to the target base station 4 d-03.When the terminal 4 d-01 receives the message, it stopstransmitting/receiving data to/from the source base station 4 d-02 andstarts the T304 timer (at step 4 d-35). If the terminal 4 d-01 fails theHO to the target base station 4 d-03 for a predetermined time, the T304timer returns to the original establishment of the terminal 4 d-01 andswitches to the RRC Idle state. The source base station 4 d-02 transmitsa SN status for the uplink/downlink data and transmits it to the targetbase station 4 d-03 if there is downlink data (at steps 4 d-40, 4 d-45).In step 4 d-30, when the terminal 4 d-01 receives the indicator, itperforms the RACH-less HO operation. That is, the terminal 4 d-01 doesnot perform an RAP such as in steps 4 c-40 and 4 c-45 in FIG. 4C andtransmits an RRC message (RRConnectionReconfigurationComplete) as theuplink resource of the target base station 4 d-03 included in the RRCmessage (RRConnectionReconfiguration) at step 4 d-30 to the target basestation 4 d-03, including the C-RNTI (Cell Radio Network TemporaryIdentifier) information (at step 4 d-50). The target base station 4 d-03can forward msg4 for confirming the reception of the RRC messagecorresponding to the msg3 through the PDCCH (at step 4 d-55). The msg4PDCCH signal is transmitted to the C-RNTI received in msg3 and includesuplink resource information.

If the RRC message 4 d-30 does not include an indication indicating toperform the RACH-less HO, the terminal 4 d-01 performs an HO operationas shown in FIG. 4C (at step 4 d-30). When the HO procedure issuccessfully completed as described above, the terminal 4 d-01 ends theT304 timer (at step 4 d-60). The target base station 4 d-03 requests thepath modification to modify the path of the bearers established in thesource base station 4 d-02 (at steps 4 d-60, 4 d-65) and notifies thesource base station 4 d-02 that the UE context of the terminal 4 d-01 isdeleted (at step 4 d-70).

FIG. 4E is a diagram of a method for performing a RACH-less HO, inaccordance with an embodiment of the present disclosure.

In FIG. 4D, the source base station 4 e-02 may request to the terminal 4e-01 the UE capability information using a UECapabilityEnquiry message(at step 4 e-05). The terminal 4 e-01 can report whether to supportRACH-less HO for each band or band combination to the source basestation 4 e-02 using the UECapabilityInformation message (at step 4e-10). If the source base station 4 e-02 also supports the RACH-less HOfor each band or band combination, the RACH-less HO may be used. Theterminal 4 e-01 in the connection mode state reports the cellmeasurement information to a source base station (source eNB) 4 e-02when the periodic or specific event is satisfied (at step 4 e 15). Basedon the measurement information, the source base station 4 e-02determines whether to perform an HO to neighboring cells. When thesource base station 4 e-02 determines the HO, the source base station 4e-02 sends an HO request message to a new base station, i.e., a targetbase station (target eNB) 4 e-03 that services a service to the terminal4 e-01 to request the HO (at step 4 e-20). The source base station 4e-02 additionally determines whether the target base station 4 e-03applies RACH-less HO to the terminal 4 e-01 supporting the RACH-less HO,and then requests HO to the target base station 4 e-03 (at step 4 e-20).In addition, when the HO is requested, it may include an indication(Indication 1) indicating whether to apply the RACH-less HO. If thetarget base station 4 e-03 accepts the HO request, it transmits the HOrequest ACK message to the source base station 4 e-02 (at step 4 e-25).The HO request Ack message includes the configuration information of atarget base station 4 e-03 necessary for HO. The configurationinformation may include an indication (indication 2) that RACH-less HOis supported when the target base station 4 e-03 supports the RACH-lessHO. The source base station 4 e-02 instructs the terminal 4 e-01 toperform the HO to the target base station 4 e-02 using theRRCConnectionReconfiguration message (at step 4 e-30). At this time, theRRC message may include one indication (indication 2) indicating toperform the RACH-less HO. When the terminal 4 e-01 receives the message,it stops transmitting/\receiving data to/from the source base station 4e-02 and starts the T304 timer (at step 4 e-35). If the terminal 4 e-01fails to succeed the HO to the target base station 4 e-03 for apredetermined time, the T304 timer returns to the original establishmentof the terminal 4 e-01 and switches to the RRC Idle state. The sourcebase station 4 e-01 transmits a SN status for the uplink/downlink dataand transmits it to the target base station 4 e-03 if there is downlinkdata (at steps 4 e-40, 4 e-45). In step 4 e-30, when the terminal 4 e-01receives the indicator, it performs the RACH-less HO operation. That is,the terminal 4 e-01 monitors uplink resource allocation informationrepeatedly transmitted from the target base station to the PDCCH withoutperforming the RAP as shown at steps 4 c-40 and 4 c-45 in FIG. 4C. Thetarget base station 4 e-03 allocates fixed uplink resources to theterminal 4 e-01 on the PDCCH so that the terminal 4 e-01 can completethe HO procedure (at step 4 e-50). In the above step, the target basestation 4 e-03 continues to transmit the fixed uplink resourceallocation information on the PDCCH and then stops when receiving aresponse indicating that the uplink resource allocation information hasbeen successfully received from the terminal 4 e-01. When the terminal 4e-01 receives the uplink resource allocation, the terminal 4 e-01transmits a RRC message (RRConnectionReconfigurationComplete)corresponding to msg3 to the target base station 4 e-03, including theC-RNTI (at step 4 e-55). The target base station 4 e-03 can forward msg4for confirming the reception of the RRC message corresponding to themsg3 through the PDCCH (at step 4 e-60). The present disclosure proposestwo methods of transmitting the PDCCH signal (msg4).

Option 1: When the target base station 4 e-03 successfully receives theRRC message (msg3), a method can include scheduling an uplink resourceallocation (grant) having parameters different from an uplink resourceallocation previously transmitted to the terminal.

Option 2: If the target base station 4 e-03 successfully receives theRRC message (msg3), a method can include scheduling downlink resourceallocation.

When Option 1 is used, there is a restriction that parameters should beset to be scheduled in the same physical resource block (PRB) wheninitial uplink resource allocation is performed in the target basestation 4 e-03. That is, the terminal 4 e-01 should repeatedly transmitthe same parameters continuously for the same resource allocation beforethe terminal 4 e-01 receives the uplink resource. On the other hand,when the Option 2 is used, there is a degree of freedom in initialuplink resource allocation in the target base station 4 e-03. That is,since the terminal 4 e-01 can know that the HO operation is completedwhen receiving the downlink resource allocation in the PDCCH, theterminal 4 e-01 can identify the uplink resource allocation bytransmitting another uplink resource allocation from the target basestation 4 e-03. In addition, the terminal 4 e-01 may include UEContention Resolution Identity in the MAC control element (CE) upon thedownlink transmission for clear operation.

If the RRC message at step 4 e-30 does not include an indicationindicating to perform the RACH-less HO, the terminal 4 e-01 performs anHO operation as shown in FIG. 4C (at step 4 e-30). When the HO procedureis successfully completed as described above, the terminal 4 e-01 endsthe T304 timer (at step 4 e-65). The target base station 4 e-03 requeststhe path modification to modify the path of the bearers established inthe source base station 4 e-02 (at steps 4 e-70, 4 e-75) and notifiesthe source base station 4 e-02 that the UE context of the terminal 4e-01 is deleted (at step 4 e-80).

FIG. 4F is a diagram of a PDCCH structure corresponding to mgs4, inaccordance with an embodiment of the present disclosure.

In the first operation and the second operation of the presentdisclosure, RACH-less HO is premised, that is, the connection isestablished through the uplink resource previously allocated from thetarget base station by directly sending theRRCConnectionReconfigurationComplete message without performing the RAPwhen the terminal performs HO from the source base station to the targetbase station. The terminal can receive the reception acknowledgment ofthe RRC message corresponding to the msg3 on the PDCCH, and Option 1 andOption 2 for sending the msg4.

Option 1 has the same PDCCH structure as in the existing LTE, and theuplink resource grant has a value different from the uplink resourcegrant that was transmitted in the previous step. In Option 2, the PDCCHdownlink resource allocation (grant) corresponding to the msg4 istransmitted to inform that the msg3 transmitted by the terminal issuccessfully received. If the terminal receives the acknowledgmentmessage, the MS performs uplink transmission through uplink resourceallocation previously transmitted by the base station. A MAC CE composedof UE contention resolution identity having a length of 6 bytes istransmitted to the MAC PDU of the PDCCH (4 f-05). In addition, theRRCConnectionReconfigurationComplete message received in msg3 may becopied and used in the payload of the UE contention resolution identityconfiguration content (payload) of the MAC CE. The RRC message requiresat least the following 3 bytes.

PDPC header (4 f-10): 1 byte

RLC header (4 f-15): 2 bytes

Payload: RRC transaction identifier (2 bits) (4 f-20)+other bits needsfor the extension containers (4 f-25)

If the RRCConnectionReconfigurationComplete message cannot be completelyrepresented by 6 bytes, the RRCConnectionReconfigurationComplete messagemay be composed of only 48 bits and the remaining bits may be discarded.The above operation is similar to the method of configuring the UEcontention resolution identity MAC CE in the LTE, and can use existingmethods. Alternatively, a new MAC CE having the same structure andpurpose as the UE contention resolution identity MAC CE may be definedand used.

FIG. 4G is a flowchart of a method of a terminal for performing anRACH-less HO, in accordance with an embodiment of the presentdisclosure.

First, it is assumed that the terminal is connected to the source basestation to transmit/receive data. The terminal in the connected mode mayinstruct the current source base station to perform the HO based on themeasurement information and may receive the HO command from the targetbase station through the RRCConnectionReconfiguration message (at step 4g-02). The terminal receiving the HO message starts a T304 timer (atstep 4 g-05), performs an HO process, and stops if the HO procedure iscompleted (at steps 4 g-40, 4 g-70, 4 g-90). The HO operation can beperformed differently depending on whether the RRC message includes anindicator indicating the RACH-less HO to the target cell.

If there is no RACH-less HO indication in theRRCConnectionReconfiguration message, the existing LTE HO proceduredescribed in FIG. 4C is performed. The terminal transmits a randomaccess preamble (at step 4 g-15), receives an RAR from the target BS,and identifies uplink resource allocation (at step 4 g-20). The terminalgenerates a msg3 signal including a C-RNTI to notify the target basestation of the completion of the HO procedure (at step 4 g-25), andtransmits the HO complete message to the target base station byincluding the HO complete message in theRRCConnectionReconfigurationComplete message (at step 4 g-30). The msg4for identifying the reception of the RRC message corresponding to themsg3 is received through the PDCCH (at step 4 g-35). The PDCCH istransmitted to the C-RNTI transmitted from the msg3 and includes theuplink resource allocation information. As described above, if the RAPfrom the target base station is successfully completed in the MAC, theterminal ends the T304 timer (at step 4 g-40).

If the RACH-less HO indicator is in the RRCConnectionReconfigurationmessage, the terminal monitors the PDCCH or the RRC to receive theuplink resource allocation. Upon receiving the uplink resourceallocation through the transmitted RRC message, a first operation of theRACH-less HO except for the RAP is performed. That is, the terminalgenerates a msg3 signal including a C-RNTI to notify the target basestation of the completion of the HO procedure (at step 4 g-55), andtransmits the HO complete message to the target base station byincluding the HO complete message in theRRCConnectionReconfigurationComplete message (at step 4 g-60). The msg4for identifying the reception of the RRC message corresponding to themsg3 is received through the PDCCH (at step 4 g-65). The PDCCH istransmitted to the C-RNTI transmitted from the msg3 and includes theuplink resource allocation information. As described above, if the RAPfrom the target base station is successfully completed in the MAC, theterminal ends the T304 timer (at step 4 g-70).

If the terminal receives the uplink resource allocation on the PDCCH instep 4 g-50, a second operation of the RACH-less HO except for the RAPis performed. The PDCCH may be repeatedly transmitted from the targetbase station. In particular, the uplink resource allocation informationincluded in the PDCCH may have the same value or different values untilthe terminal transmits msg3. The terminal generates a msg3 signalincluding a C-RNTI to notify the target base station of the completionof the HO procedure (at step 4 g-75), and transmits the HO completemessage to the target base station by including the HO complete messagein the RRCConnectionReconfigurationComplete message (at step 4 g-80).The msg4 for identifying the reception of the RRC message correspondingto the msg3 is received through the PDCCH (at step 4 g-85). The PDCCH istransmitted to the C-RNTI transmitted in the msg3, and the method foridentifying the reception of the msg3 can include one of the followingtwo methods.

Option 1: When the target base station successfully receives the RRCmessage (msg3), a method can include scheduling an uplink resourceallocation (grant) having parameters different from an uplink resourceallocation previously transmitted to the terminal.

Option 2: If the target base station successfully receives the RRCmessage (msg3), a method can include scheduling downlink resourceallocation.

When Option 1 is used, there is a restriction that parameters should beset to be scheduled in the same PRB when initial uplink resourceallocation is performed in the target cell. That is, the terminal shouldrepeatedly transmit the same parameters continuously for the sameresource allocation before the terminal receives the uplink resource. Onthe other hand, when Option 2 is used, there is a degree of freedom ininitial uplink resource allocation in the target cell. That is, sincethe terminal can know that the HO operation is completed when receivingthe downlink resource allocation in the PDCCH, the terminal can identifythe uplink resource allocation by transmitting another uplink resourceallocation from the target base station. In addition, the UE ContentionResolution Identity may be included in the MAC CE upon the downlinktransmission for clear operation. The MAC CE design method is describedin detail with reference to FIG. 4F. As described above, if the RAP fromthe target base station is successfully completed in the MAC, theterminal ends the T304 timer (at step 4 g-90).

FIG. 4H is a diagram of the terminal, according to an embodiment of thepresent disclosure.

Referring to FIG. 4H, the terminal includes a transceiver 4 h-05, acontroller 4 h-10, a multiplexer and demultiplexer 4 h-15, a controlmessage processor 4 h-30, various higher layer processors 4 h-20 and 4h-25, an EPS bearer manager 4 h-35, and a NAS layer apparatus 4 h-40.

The transceiver 4 h-05 receives data and a predetermined control signalthrough a forward channel of the serving cell and transmits the data andthe predetermined control signal through a the reverse channel. When aplurality of serving cells are configured, the transceiver 4 h-05transmits and receives data and a control signal through the pluralityof carriers.

The multiplexer and demultiplexer 4 h-15 serves to multiplex datagenerated from the upper layer processors 4 h-20 and 4 h-25 or thecontrol message processor 4 h-30 or demultiplex data received by thetransceiver 4 h-05 and transmit the data to the appropriate upper layerprocessors 4 h-20 and 4 h-25 or the control message processor 4 h-30.

The control message processor 4 h-30 is an RRC layer apparatus andprocess the control message received from the base station to take therequired operation. For example, when receiving an RRC CONNECTION SETUPmessage, it configures an SRB and a temporary DRB.

The upper layer processors 4 h-20 and 4 h-25 are the DRB apparatus andmay be configured for each service. The higher layer processors 4 h-20and 4 h-25 process data generated from user services such as a filetransfer protocol (FTP) or a VoIP and transfer the processed data to themultiplexer and demultiplexer 4 h-15 or process the data transferredfrom the multiplexer and demultiplexer 4 h-15 and transfer the processeddata to service application of the higher layer. One service may bemapped one-to-one with one evolved packet system (EPS) bearer and onehigher layer processor on a one-to-one basis.

The controller 4 h-10 confirms scheduling commands, for example, reversegrants, received through the transceiver 4 h-05 to control thetransceiver 4 h-05 and the multiplexer and demultiplexer 4 h-15 toperform the reverse transmission by an appropriate transmission resourceat an appropriate time.

FIG. 4I is a diagram of a base station, MME, and S-GW, according to anembodiment of the present disclosure.

The base station of FIG. 4I includes a transceiver 4 i-05, a controller4 i-10, a multiplexer and demultiplexer 4 i-20, a control messageprocessor 4 i-35, various upper layer processors 4 i-25 and 4 i-30, ascheduler 4 i-15, EPS bearer apparatuses 4 i-40 and 4 i-45, and a NASlayer apparatus 4 i-50. The EPS bearer apparatuses 4 i-40 and 4 i-45 arelocated on the S-GW and the NAS layer apparatus is located on the MME.

The transceiver 4 i-05 transmits data and a predetermined control signalthrough a forward carrier and receives the data and the predeterminedcontrol signal through a reverse carrier. When a plurality of carriersare configured, the transceiver 4 i-05 transmits and receives the dataand the control signal through the plurality of carriers.

The multiplexer and demultiplexer 4 i-20 serves to multiplex datagenerated from the upper layer processors 4 i-25 and 4 i-30 or thecontrol message processor 4 i-35 or demultiplex data received by thetransceiver 4 i-05 and transmit the data to the appropriate upper layerprocessors 4 i-25 and 4 i-30 or the control message processor 4 i-35 orthe controller 4 i-10. The control message processor 4 i-35 allows theUE to process the transmitted control message to perform the requiredoperation or generates the control message to be transmitted to the UEand transmits the generated control message to the lower layer.

The higher layer processors 4 i-25 and 4 i-30 may be configured for eachEPS bearer and configure data transferred from the EPS bearerapparatuses 4 i-40 and 4 i-45 as the RLC PDU and may transfer the datato the multiplexer and demultiplexer 4 i-20 or configure RLC PDUtransferred from the multiplexer and demultiplexer 4 i-20 as the PDCPSDU and transfer the RLC PDU to the EPS bearer apparatuses 4 i-40 and 4i-45.

The scheduler 4 i-15 allocates a transmission resource to the terminalat appropriate timing in consideration of the buffer status and thechannel status of the terminal, etc. and allows the transceiver toprocess the signal transmitted from the terminal or perform a process totransmit a signal to the terminal.

The EPS bearer apparatuses 4 i-40 and 4 i-45 are configured for each EPSbearer, and processes the data transmitted from the higher layerprocessor and transmits the processed data to the next network node.

The upper layer processors 4 i-25 and 4 i-30 and the EPS bearerapparatuses 4 i-40 and 4 i-45 are connected to each other by the S1-Ubearer. The higher layer processor corresponding to the common DRB isconnected to the EPS bearer for the common DRB by a common S1-U bearer.

The NAS layer apparatus 4 i-50 processes the IP packet included in theNAS message and transmits the processed IP packet to the S-GW.

A method for determining and identifying a successful uplink resourceallocation of a terminal in an HO when a random access is not used.

1. A method of receiving an indicator indicating that a terminal doesnot use random access.

A method for receiving the indication through an RRC message (HOcommand) of a source base station;

2. A method for making an operation different according to whether theindication is received.

A method for performing the existing LTE HO procedure when the indicatoris not included;

A method for not using a random access for an HO to a target basestation when the indicator is included;

3. A method for performing a first operation and a second operation ofan HO without a random access according to a method for receiving uplinkresource allocation information.

A method for allowing a terminal to receive resource allocationinformation to an RRC message (HO command) by a first operation;

A method for allowing a terminal to receive uplink resource allocationinformation on a PDCCH by a second operation;

The first operation receives the uplink resource allocation by the RRCmessage to omit the random access operation;

A method for performing an HO procedure of the existing LTE afteromitting the random access in the first operation;

A method for omitting, by a terminal, a random access and receivinguplink resource allocation (msg2) on a PDCCH in the second operation;

A method for repeatedly transmitting the same uplink resource allocationby allowing a base station to use the same parameter for the msg2 of thesecond operation;

A method for generating and transmitting msg3 including C-RNTI of aterminal in the second operation;

A method for differently operating option 1 and option 2 in a method forreceiving msg4 in the second operation;

An object to notify that the msg4 of the second operation successfullyreceives the msg3 transmitted by the terminal;

A method for receiving a resource allocation value different from anuplink resource already received on a PDCCH in the option 1 of thesecond operation;

A method for including downlink resource allocation information in theoption 2 of the second operation;

A method for including “UE Contention Resolution Identity” in MAC PDU ofthe downlink resource allocation information;

A method for allowing the “UE Contention Resolution Identity” to includea content of the RRC message received in the msg3;

The “UE Contention Resolution Identity” reuses the existing LTEstructure or uses a new MAC CE;

A method for including only initial 48 bit information when the contentof the msg3 exceeds 48 bits.

The present disclosure relates to a mobile communication system, andmore particularly, to a method and apparatus for determining priority ofuplink and downlink transmission links and side links in an LTE terminalsupporting vehicle-to-everything (V2X).

FIG. 5A is a diagram of the LTE system, in accordance with an embodimentof the present disclosure.

Referring to FIG. 5A, the wireless communication system is configured toinclude a plurality of base stations 5 a-05, 5 a-10, 5 a-15, and 5 a-20,an MME 5 a-25, an S-GW 5 a-30. UE or terminal 5 a-35 accesses anexternal network through the base stations 5 a-05, 5 a-10, 5 a-15, and 5a-20 and the S-GW 5 a-30.

The base stations 5 a-05, 5 a-10, 5 a-15, and 5 a-20 are access nodes ofa cellular network and provides a wireless access to terminals that areconnected to a network. That is, in order to serve traffic of users, thebase stations 5 a-05, 5 a-10, 5 a-15, and 5 a-20 collect stateinformation such as a buffer state, an available transmission powerstate, a channel state, or the like of the terminals to performscheduling, thereby supporting a connection between the terminals and acore network (CN). The MME 5 a-25 is an apparatus for performing variouscontrol functions as well as a mobility management function for theterminal 5 a-35 and is connected to a plurality of base stations 5 a-05,5 a-10, 5 a-15, and 5 a-20, and the S-GW 5 a-30 is an apparatus forproviding a data bearer. Further, the MME 5 a-25 and the S-GW 5 a-30 mayfurther perform authentication, bearer management, etc., on the terminal5 a-35 connected to the network and may process packets that are to bereceived from the base stations 5 a-05, 5 a-10, 5 a-15, and 5 a-20 andpackets that are to be transmitted to the base stations 5 a-05, 5 a-10,5 a-15, and 5 a-20.

FIG. 5B is a diagram of a radio protocol structure in the LTE system, inaccordance with an embodiment of the present disclosure.

Referring to FIG. 5B, the radio protocol of the LTE system is configuredto include PDCPs 5 b-05 and 5 b-40, RLCs 5 b-10 and 5 b-35, and MACs 5b-15 and 5 b-30 in the terminal and the eNB, respectively. The PDCPs 5b-05 and 5 b-40 control IP header compression/decompression. The mainfunctions of the PDCP are summarized as follows.

Header compression and decompression function (Header compression anddecompression: ROHC only)

Transfer function of user data (Transfer of user data)

In-sequence delivery function (In-sequence delivery of upper layer PDUsat PDCP re-establishment procedure for RLC AM)

Reordering function (For split bearers in DC (only support for RLC AM):PDCP PDU routing for transmission and PDCP PDU reordering for reception)

Duplicate detection function (Duplicate detection of lower layer SDUs atPDCP re-establishment procedure for RLC AM)

Retransmission function (Retransmission of PDCP SDUs at HO and, forsplit bearers in DC, of PDCP PDUs at PDCP data-recovery procedure, forRLC AM)

Ciphering and deciphering function (Ciphering and deciphering)

Timer-based SDU discard function (Timer-based SDU discard in uplink)

The RLCs 5 b-10 and 5 b-35 reconfigures the PDCP PDU to an appropriatesize to perform the ARQ operation or the like. The main functions of theRLC are summarized as follows.

Data transfer function (Transfer of upper layer PDUs)

ARQ function (Error Correction through ARQ (only for AM data transfer))

Concatenation, segmentation, reassembly functions (Concatenation,segmentation and reassembly of RLC SDUs (only for UM and AM datatransfer))

Re-segmentation function (Re-segmentation of RLC data PDUs (only for AMdata transfer))

Reordering function (Reordering of RLC data PDUs (only for UM and AMdata transfer)

Duplicate detection function (Duplicate detection (only for UM and AMdata transfer))

Error detection function (Protocol error detection (only for AM datatransfer))

RLC SDU discard function (RLC SDU discard (only for UM and AM datatransfer))

RLC re-establishment function (RLC re-establishment)

The MACs 5 b-15 and 5 b-30 are connected to several RLC layer devicesconfigured in one terminal and perform multiplexing RLC PDUs into an MACPDU and demultiplexing the RLC PDUs from the MAC PDU. The main functionsof the MAC are summarized as follows.

Mapping function (Mapping between logical channels and transportchannels)

Multiplexing/demultiplexing function (Multiplexing/demultiplexing of MACSDUs belonging to one or different logical channels into/from TBsdelivered to/from the physical layer on transport channels)

Scheduling information reporting function (Scheduling informationreporting)

HARQ function (Error correction through HARQ)

Priority handling function between logical channels (Priority handlingbetween logical channels of one UE)

Priority handling function between terminals (Priority handling betweenUEs by means of dynamic scheduling)

MBMS service identification function (MBMS service identification)

Transport format selection function (Transport format selection)

Padding function (Padding)

Physical layers 5 b-20 and 5 b-25 perform channel-coding and modulatinghigher layer data, making the higher layer data as an OFDM symbol andtransmitting them to a radio channel, or demodulating andchannel-decoding the OFDM symbol received through the radio channel andtransmitting the demodulated and channel-decoded OFDM symbol to thehigher layer.

Although not illustrated, RRC layers are present at an upper part of thePDCP layer of the terminal and the base station, and the RRC layer mayreceive and transmit connection and measurement related control messagesfor a radio resource control.

FIG. 5C is a diagram of vehicle-to-everything (V2X) communication withina cellular system, in accordance with an embodiment of the presentdisclosure.

A V2X is a communication technology through a vehicle and allinterfaces, and examples thereof may include a vehicle-to-vehicle (V2V),vehicle-to-infra-structure (V2I), a vehicle-to-pedestrian (V2P), and thelike according to the form thereof and the component forming thecommunication. The V2P and V2V depends on a structure and an operationprinciple of device-to-device (D2D).

The base station 5 c-01 includes at least one vehicle terminal 5 c-05and 5 c-10 and a pedestrian portable terminal 5 c-15 located in a cell 5c-02 supporting V2X. That is, the vehicle terminal 5 c-05 performscellular communication using the base station 5 c-01 and the vehicleterminal-base link 5 c-30 and 5 c-35 or the device-to-devicecommunication using side links 5 c-20 and 5 c-25 with the other vehicleterminal 5 c-10 or the pedestrian portable terminal 5 c-15. In order forthe vehicle terminals 5 c-05 and 5 c-10 and the pedestrian portableterminal 5 c-15 to directly transmit and receive information using theside links 5 c-20 and 5 c-25, the base station 5 c-01 should allocate aresource pool that may be used for the side link communication. It maybe divided into a scheduled resource allocation (mode 3) and UEautonomous resource allocation (mode 4), by a base station. In the caseof the scheduled resource allocation, the base station allocatesresources used for the side link transmission to the RRC-connected UEsin a dedicated scheduling manner. The above method is effective forinterference management and resource pool management (semi-persistencetransmission) because the base station 5 c-01 can manage the resourcesof the side link.

In addition, in the case of the scheduled resource allocation (mode 3)in which a base station 5 c-01 assigns and manages resources for theV2P, if an RRC-connected terminal has data to be transmitted to anotherterminal, the data may be transmitted to the base station 5 c-01 usingthe RRC message or the MAC control element (MAC CE). Here, for the RRCmessage, SidelinkUEInformation and UEAssistanceInformation message maybe used. The MAC CE may be, for example, a buffer status report MAC CEin a new format (including an indicator that notifies at least a bufferstatus report for at least V2P communication and information on a sizeof data that are buffered for D2D communication). The detailed formatand content of the buffer status report used in the 3GPP refer to 3GPPstandard TS36.321 E-UTRA MAC Protocol Specification.

On the other hand, in the UE autonomous resource allocation, the basestation 5 c-01 provides the side link transmission/reception resourcepool for V2X as the system information, and the terminal selects theresource pool according to the predetermined rule. The resourceselection method may include resource selection based on zone mappingand sensing, random selection, or the like. In the structure of theresource pool for V2X, one sub channel may be configured by allowingresources 5 c-40, 5 c-50, and 5 c-60 for scheduling allocation (SA) andresources 5 c-45, 5 c-55, and 5 c-65 for data transmission to beadjacent to each other and the resources for SAs 5 c-70, 5 c-75 and 5c-80 and data 5 c-85, 5 c-90 and 5 c-95 may be used in a manner notadjacent to each other. Whichever of the above two structures is used,the SA consists of two consecutive PRBs and contains content indicatingthe location of the resource for the data. The number of terminalsreceiving the V2X service in one cell may be many and the relationshipbetween the base station 5 c-01 and the terminals 5 c-05, 5 c-10, and 5c-15 as described above may be extended and applied.

FIG. 5D is a diagram of a data transmission procedure of a V2X terminaloperated in a mode 3, in accordance with an embodiment of the presentdisclosure.

A terminal 5 d-01 that is camped at step 5 d-05 receives the systeminformation block 21 (SIB21) from the base station 5 d-03. The systeminformation includes resource pool information for transmission andreception, configuration information for sensing operation, informationfor setting synchronization, information for transmitting/receivinginter-frequency, and the like. When data traffic for V2X is generated(at step 5 d-15) in the terminal 5 d-01, an RRC connection with the basestation 5 d-01 is performed (at step 5 d-20). The above RRC connectionprocess may be performed before the data traffic is generated (at step 5d-15). The terminal 5 d-01 requests the base station 5 d-03 fortransmission resources capable of performing V2X communication with theother terminal 5 d-02 (at step 5 d-25). The terminal 5 d-01 may requestthe base station 5 d-03 using the RRC message or the MAC CE. Here, asthe RRC message, SidelinkUEInformation, UEAssistanceInformation messagemay be used. The MAC CE may be, for example, a buffer status report MACCE in a new format (including indicator that notifies at least a bufferstatus report for at least V2X communication and information on a sizeof data that are buffered for D2D communication). The base station 5d-03 allocates a V2X transmission resource to the terminal 5 d-01through a dedicated RRC message (at step 5 d-30). The message may beincluded in the RRCConnectionReconfiguration message. The resourceallocation may be a V2X resource through the vehicle terminal-base link5 c-30 or a resource for the side links 5 c-20 and 5 c-25 according tothe type of traffic requested by the terminal 5 d-01 or the congestionof the corresponding link. In order to make the above determination, theterminal 5 d-01 additionally transmits prose per packet priority (PPPP)or logical channel ID (LCID) information of V2X traffic throughUEAssistanceInformation or MAC CE. Since the base station 5 d-03 alsoknows information about resources used by other terminals, the basestation 5 d-03 schedules the resources requested by the terminal 5 d-01among the remaining resources. If the SPS configuration information viathe vehicle terminal-base link 5 c-30 is included in the RRC message,the SPS can be activated by DCI transmission on the PDCCH (at step 5d-35). The terminal 5 d-01 selects a transmission link and a resourceaccording to the resource and transmission method allocated from thebase station 5 d-03 (at step 5 d-40) and transmits the data to theterminal 5 d-02 (at step 5 d-45).

FIG. 5E is a diagram of a data transmission method of a V2X terminaloperated in a mode 4, in accordance with an embodiment of the presentdisclosure.

Unlike the mode 3 in which the base station 5 e-03 directly participatesin resource allocation, the mode 4 operation is different from the mode3 operation in that the terminal 5 e-01 autonomously selects a resourcebased on the resource pool received in advance through the systeminformation and transmits the data. In the V2X communication, the basestation 5 e-03 allocates various kinds of resource pools (V2V resourcepool, V2P resource pool) for the terminal 5 e-01. The resource poolincludes a resource pool for autonomously selecting an availableresource pool after a terminal senses resources used by nearbyterminals, and a resource pool in which a terminal randomly selectsresources from a resource pool established in advance, or the like.

The terminal 5 e-01 that is camped at step 5 e-05 receives the SIB21from the base station 5 e-03 (at step 5 e-10). The system informationincludes resource pool information for transmission and reception,configuration information for sensing operation, information for settingsynchronization, information for transmitting/receiving inter-frequency,and the like. If the data traffic for V2X is generated in the terminal 5e-01 (at step 5 e-15), the terminal 5 e-01 selects the resource in thetime/frequency region (at step 5 e-20) and transmits data to otherterminals 5 e-02 according to the transmission operation (dynamicallocation one-time transmission, dynamic allocation multipletransmission, sensing based one-time transmission, sensing basedmultiple transmission, random transmission) established in the resourcepool transmitted from the base station 5 e-03 through the systeminformation (at step 5 e-25).

The terminal 5 e-01 supporting the LTE V2X may perform the V2Xcommunication through the side link PC5 and the LTE uplink (UL)/downlink(DL) (i.e., resource for the side links 5 c-20 and 5 c-25 or a vehicleterminal-base link 5 c-30). The terminal 5 e-01 needs a plurality of RFchains for the reception of the LTE downlink and the side link, and thetype and number of V2X services that can be received according to thenumber of RF chains held by the terminal 5 e-01 are determined.Referring to the transmission capability of the terminal 5 e-01, theterminal 5 e-01 can have a plurality of RF chains or share one RF chainfor LTE uplink and side link transmission. The terminal 5 e-01supporting the LTE V2X should appropriately perform the path switchingor the power allocation when the LTE uplink and side link traffics aresimultaneously generated, based on the following:

Case 1: Separated Tx chain for the uplink transmission and the side linktransmission is present and the power limitation is present separately;

Case 2: Separated Tx chain for the uplink transmission and the side linktransmission is present and the power limitation is shared; and

Case 3: Power limitation is shared with Tx chain for the uplinktransmission and the side link transmission.

The transmission method can be changed according to the Tx chaincapability of the terminal in the above situations. In Case 1, since theuplink transmission and the side link transmission do not affect eachother because they are independent of the number of Tx chains and power,they are operated independently of the priorities of LTE UL/DL and PC5(i.e., vehicle terminal-base link 5 c-30 or a resource for the sidelinks 5 c-20 and 5 c-25). In case 2, the uplink transmission and theside link transmission use a separated Tx chain, but because power isshared, a method of reallocating transmission power according topriority is needed. In Case 3, both the Tx chain selection and the powerreallocation should be considered according to the priorities of the LTEUL/DL and the PC5, since the uplink transmission and the side linktransmission share both the Tx chain and power. In particular, whenthere is one Tx chain, it is necessary to define the priority in orderto switch and transmit the path according to the priority of the LTEUL/DL and the PC5. In the present disclosure, in order to clearly definethe priorities of the LTE UL/DL and the PC5, it is assumed that there isone RF Tx chain in Case 3. However, the operation proposed below can beextended to other cases, and can be applied, and may be applied to theTx chain selection and the power reallocation according to thepriorities of the LTE UL/DL and the PC5 described herein. In addition,the V2X operation proposed herein is based on the mode 4 operation. Inthe case of the mode 3, the base station 5 e-03 can schedule resourcesto manage the LTE UL/DL and PC5 traffics that are simultaneouslygenerated.

FIG. 5F is a flowchart of a first operation of the terminal according topriority of LTE UL/DL and PC5 (i.e., vehicle terminal-base link 5 c-30or a resource for the side links 5 c-20 and 5 c-25), in accordance withan embodiment of the present disclosure.

The terminal supporting LTE V2X receives the SIB21 from the base station(at step 5 f-05). The system information includes resource poolinformation for transmission and reception, configuration informationfor sensing operation, information for setting synchronization,information for transmitting/receiving inter-frequency, and the like. Ifthe data traffic for the V2X is generated in the terminal (at step 5f-10), the terminal selects the resources in the time/frequency regionin the side link transmission resource pool and transmits data to otherterminals, according to the transmission operation (dynamic allocation,sensing based transmission, random transmission) established in theresource pools transmitted through the system information of the basestation (at step 5 f-15). When the transmission for the uplink and thetransmission for the side link are simultaneously generated in theterminal, that is, when the LTE UL/DL transmission and the PC5transmission for the V2X side link that are required for the existingLTE uplink, the terminal is operated according to the predeterminedpriority. In the present disclosure, the priority of the Uu and PC5transmission of the terminal supporting the LTE V2X is defined asfollows.

1. Uplink transmission when the random access is generated.

2. Sidelink transmission having high priority (the side link traffic ofthe PPPP larger than the predetermined PPPP threshold value).

3. Uplink transmission other than the random access.

4. Sidelink transmission having low priority (the side link traffic ofthe PPPP smaller than the predetermined PPPP threshold value).

Based on the priority of the LTE UL/DL and PC5 transmissions, it ischecked whether there is a random access among the Uu and PC5 trafficsgenerated simultaneously (at step 5 f-25). If the LTE UL/DL traffic israndom access, the terminal performs the random access through the LTEUL/DL regardless of the PPPP. The random access serves to maintain thesynchronization and RRC connection for the LTE uplink/downlinktransmission and reception, and if the random access is not performed,the entire operation of the LTE uplink/downlink transmission/receptionis not performed smoothly, so it should be operated at the highestpriority.

The terminal transmits a preamble corresponding to the preamble IDprovided from the base station or the randomly selected preamble ID tothe cell (at step 5 f-30). After a certain number of subframes havepassed after the preamble is transmitted, the terminal monitors whethera RAR is transmitted from the cell. The time period in which themonitoring is performed is referred to as a RAR window. If the RAR isreceived for the specific time (at step 5 f-35), the terminal completesthe random access procedure, again confirms whether there isinterference between the LTE UL/DL and PC5 transmission, and thenrepeats the operation. The RAP may be completed after the transmissionof msg1 in the uplink transmission view. That is, the operation may bemade without performing step 5 f-35.

In step 5 f-40, the terminal compares the PPPP of the V2X side linktraffic with the preset PPPP threshold. The PPPP threshold value may bereceived by the system information of the base station or the RRCmessage or may be a value preset in the terminal. If the PPPP of thegenerated V2X side link traffic is greater than the threshold value, theterminal performs the V2X side link (PC5) transmission (at step 5 f-45).If the V2X side link transmission is completed, the terminal performsthe LTE uplink transmission (at step 5 f-50). This is because the V2Xtransmission having high priority is overall associated with safety andhas low latency requirements. If the PPPP of the V2X side link trafficgenerated in step 5 f-40 is smaller than the threshold value, theterminal performs the LTE uplink transmission (at step 5 f-55). If theuplink transmission is completed, the V2X side link transmission isperformed (at step 5 f-60).

FIG. 5G is a flowchart of a second operation of the terminal accordingto priority of LTE UL/DL and PC5, in accordance with an embodiment ofthe present disclosure.

The terminal supporting LTE V2X receives the SIB21 from the base station(at step 5 g-05). The system information includes resource poolinformation for transmission and reception, configuration informationfor sensing operation, information for setting synchronization,information for transmitting/receiving inter-frequency, and the like. Ifthe data traffic for the V2X is generated in the terminal (at step 5g-10), the terminal selects the resources in the time/frequency regionin the side link transmission resource pool and transmits data to otherterminals, according to the transmission operation (dynamic allocation,sensing based transmission, random transmission) established in theresource pools transmitted through the system information of the basestation (at step 5 g-15). When the transmission for the uplink and thetransmission for the side link are simultaneously generated in theterminal, that is, when the LTE UL/DL transmission and the PC5transmission for the V2X side link that are required for the existingLTE uplink, the terminal is operated according to the predeterminedpriority. The priority of the LTE UL/DL and PC5 transmission of theterminal supporting the LTE V2X is defined as follows.

1. Uplink transmission when the random access is generated.

2. Sidelink transmission having high priority (side link traffic of PPPPlarger than the predetermined PPPP threshold value).

3. Uplink transmission other than the random access.

4. Sidelink transmission having low priority (the side link traffic ofthe PPPP smaller than the predetermined PPPP threshold value).

Based on the priority of the LTE UL/DL and PC5 transmissions, it ischecked whether there is a random access among the LTE UL/DL and PC5traffics generated simultaneously (at step 5 g-25). If the LTE UL/DLtraffic is random access, the terminal performs the random accessthrough the LTE UL/DL regardless of the PPPP. The random access servesto maintain the synchronization and RRC connection for the LTE UL/DLtransmission and reception, and if the random access is not performed,the entire operation of the LTE UL/DL transmission/reception is notperformed smoothly, so it should be operated at the highest priority.The terminal transmits a preamble corresponding to the preamble IDprovided from the base station or the randomly selected preamble ID tothe cell (at step 5 g-30). After a certain number of subframes havepassed after the preamble is transmitted, the terminal monitors whethera RAR is transmitted from the cell. The time period in which themonitoring is performed is referred to as a RAR window. If the RAR isreceived for the specific time (at step 5 g-35), the terminal generatesthe RRC message (msg3) and transmits the generated RRC message to thebase station (at step 5 g-40).

Upon receiving the PDCCH corresponding to the msg4 from the basestation, the terminal terminates the RAP (at step 5 g-45). The PDCCH istransmitted as a temporary C-RNTI value, and the received MAC PDUincludes the UE contention resolution identity information in the MACCE. The terminal completes the RAP, again confirms whether there is theinterference between the LTE UL/DL and PC5 transmissions, and thereafterrepeats the operation. Since step 5 g-45 is associated with thereception of the msg4 in the RAP, the terminal may omit step 5 g-45.That is, after the msg3 transmission, the terminal may complete therandom access transmission and proceed to the next step.

In step 5 g-50, the terminal compares the PPPP of the V2X side linktraffic with the preset PPPP threshold. The PPPP threshold value may bereceived by the system information of the base station or the RRCmessage or may be a value preset in the terminal. If the PPPP of thegenerated V2X side link traffic is greater than the threshold value, theterminal performs the V2X side link (PC5) transmission (at step 5 g-55).If the V2X side link transmission is completed, the terminal performsthe LTE uplink transmission (at step 5 g-60). This is because the V2Xtransmission having high priority is overall associated with safety andhas low latency requirements. If the PPPP of the V2X side link trafficgenerated in step 5 g-50 is smaller than the threshold value, theterminal performs the LTE UL/DL transmission (at step 5 g-65). If theLTE UL/DL is completed, the V2X side link transmission is performed (atstep 5 g-70).

FIG. 5H is a diagram of the terminal, according to the embodiment of thepresent disclosure.

As shown in FIG. 5H, the terminal according to the embodiment of thepresent disclosure includes a transceiver 5 h-05, a controller 5 h-10, amultiplexer and demultiplexer 5 h-15, various upper layer processors 5h-20 and 5 h-25, and a control message processor 5 h-30.

The transceiver 5 h-05 receives data and a predetermined control signalthrough a forward channel of the serving cell and transmits the data andthe predetermined control signal through a the reverse channel. When aplurality of serving cells are configured, the transceiver 5 h-05transmits and receives data and a control signal through the pluralityof carriers. The multiplexer and demultiplexer 5 h-15 serves tomultiplex data generated from the upper layer processors 5 h-20 and 5h-25 or the control message processor 5 h-30 or demultiplex datareceived by the transceiver 5 h-05 and transmit the data to theappropriate upper layer processors 5 h-20 and 5 h-25 or the controlmessage processor 5 h-30. The control message processor 5 h-30 transmitsand receives a control message from the base station and takes necessaryactions. This includes the function of processing the RRC message andthe control messages such as the MAC CE, and includes reporting of thechannel busy ratio (CBR) measurement value and receiving the RRCmessages for the resource pool and the terminal operation. The upperlayer processors 5 h-20 and 5 h-25 mean the DRB apparatus and may beconfigured for each service. The higher layer processors 5 h-20 and 5h-25 process data generated from user services such as an FTP or a VoIPand transfer the processed data to the multiplexer and demultiplexer 5h-15 or process the data transferred from the multiplexer anddemultiplexer 5 h-15 and transfer the processed data to serviceapplication of the higher layer. The controller 5 h-10 confirmsscheduling commands, for example, reverse grants controls receivedthrough the transceiver 5 h-05 to control the transceiver 5 h-05 and themultiplexer and demultiplexer 5 h-15 to perform the reverse transmissionby an appropriate transmission resource at an appropriate time. It isdescribed above that the terminal is configured of a plurality of blocksand each block performs different functions, the controller 5 h-10,however, may also perform the function performed by the demultiplexer 5h-15.

FIG. 5I is a diagram of the base station, according to the embodiment ofthe present disclosure.

The base station apparatus of FIG. 5I includes a transceiver 5 i-05, acontroller 5 i-10, a multiplexer and demultiplexer 5 i-20, a controlmessage processor 5 i-35, various upper layer processors 5 i-25 and 5i-30, and a scheduler 5 i-15.

The transceiver 5 i-05 transmits data and a predetermined control signalthrough a forward carrier and receives the data and the predeterminedcontrol signal through a reverse carrier. When a plurality of carriersare configured, the transceiver 5 i-05 transmits and receives the dataand the control signal through the plurality of carriers. Themultiplexer and demultiplexer 5 i-20 serves to multiplex data generatedfrom the upper layer processors 5 i-25 and 5 i-30 or the control messageprocessor 5 i-35 or demultiplex data received by the transceiver 5 i-05and transmit the data to the appropriate upper layer processors 5 i-25and 5 i-30 or the control message processor 5 i-35 or the controller 5i-10.

The control message processor 5 i-35 receives the instruction of thecontroller 5 i-10, generates a message to be transmitted to theterminal, and transmits the generated message to the lower layer. Theupper layer processors 5 i-25 and 5 i-30 may be configured for eachterminal and each service and processes data generated from userservices such as FTP and VoIP and transmits the processed data to themultiplexer and demultiplexer 5 i-20 or processes data transmitted fromthe multiplexer and demultiplexer 5 i-20 and transmits the processeddata to service applications of the upper layer.

The scheduler 5 i-15 allocates a transmission resource to the terminalat appropriate timing in consideration of the buffer status and thechannel status of the terminal, the active time of the terminal, etc.and allows the transceiver to process a signal transmitted from theterminal or performs a process to transmit a signal to the terminal.

The present disclosure has the right of the following claims.

Priority determination and operation of uplink (Uu) and side link (PC5)transmission for terminals supporting both LTE and V2X.

1. A method for setting, by a terminal, a priority (PPPP) threshold ofV2X side-link traffic.

A method for receiving the above priority (PPPP) threshold value insystem information of the base station or in an RRC message;

A method of storing the priority (PPPP) threshold value as a presetvalue by the terminal;

2. A method in which a terminal checks the capability of the terminal,such as the number of RF chains and power control, and operatesaccording to priority.

A method of differently setting an operation at the time of collisionbetween the uplink and the side link differently according to theterminal capability;

A method of performing a power control according to priority when thenumber of transmission RF chains is sufficient for each link;

A method of switching the transmission of the uplink and the side linkaccording to the priority when the number of transmission RF chains isinsufficient;

3. A method for performing an operation according to priority when thereis a collision in time/frequency between uplink and side link.

A method of setting random access as the highest priority in thepriority order;

A method for transmitting, as second priority, a V2X side linktransmission of priority higher than the PPPP threshold in the priority;

A method for transmitting, as third priority, uplink transmissions otherthan the random access in the priority;

A method for transmitting, as fourth priority, a V2X side linktransmission of priority lower than the PPPP threshold in the priority;

A first operating method for including only the msg1 transmission in thehighest priority random access procedure;

A method for receiving a msg2 for the first operation;

A second operation method for including both of the msg1 and msg3transmissions in the highest priority random access procedure;

A method for receiving a msg4 for the second operation;

4. A method in which the terminal is basically operated in a mode 4.

While the present disclosure has been shown and described with referenceto certain embodiments thereof, it will be understood by those skilledin the art that various changes in form and details may be made thereinwithout departing from the scope of the present disclosure. Therefore,the scope of the present disclosure should not be defined as beinglimited to the embodiments, but should be defined by the appended claimsand equivalents thereof.

What is claimed is:
 1. A method performed by a terminal in a wirelesscommunication system, the method comprising: receiving, from a sourcebase station, a radio resource control (RRC) connection reconfigurationmessage for a random access channel-less (RACH-less) handover betweenthe source base station and a target base station; receiving, from thetarget base station, an uplink grant for the RACH-less handover based onthe RRC connection reconfiguration message by monitoring a physicaldownlink control channel (PDCCH); transmitting, to the target basestation, an RRC connection reconfiguration complete message for theRACH-less handover based on the uplink grant, the RRC connectionreconfiguration complete message being associated with a cell radionetwork temporary identifier (C-RNTI) of the terminal; and receiving,from the target base station, a medium access control (MAC) controlelement (CE) including a contention resolution identity of the terminal,as a response to the RRC connection reconfiguration complete message forcompleting the RACH-less handover, wherein the MAC CE including thecontention resolution identity is received based on a physical downlinkcontrol channel (PDCCH) addressed to the C-RNTI.
 2. The method of claim1, further comprising transmitting, to the source base station,information indicating that the terminal supports the RACH-lesshandover.
 3. The method of claim 1, wherein the RACH-less handover iscompleted based on the receiving of the MAC CE.
 4. A method performed bya target base station in a wireless communication system, the methodcomprising: receiving, from a source base station, a message requestinga random access channel-less (RACH-less) handover for a terminal;transmitting, to the terminal on a physical downlink control channel(PDCCH), an uplink grant for the RACH-less handover based on themessage; receiving, from the terminal, a radio resource control (RRC)connection reconfiguration complete message for the RACH-less handoverbased on the uplink grant, the RRC connection reconfiguration completemessage being associated with a cell radio network temporary identifier(C-RNTI) of the terminal; and transmitting, to the terminal, a mediumaccess control (MAC) control element (CE) including a contentionresolution identity of the terminal, as a response to the RRC connectionreconfiguration complete message for completing the RACH-less handover,wherein the MAC CE including the contention resolution identity istransmitted based on a physical downlink control channel (PDCCH)addressed to the C-RNTI.
 5. The method of claim 4, wherein informationindicating that the terminal supports the RACH-less handover istransmitted from the terminal to the source base station.
 6. The methodof claim 4, wherein the RACH-less handover is completed based on thereceiving of the MAC CE.
 7. A terminal in a wireless communicationsystem, the terminal comprising: a transceiver configured to transmitand receive signals; and a controller coupled with the transceiver andconfigured to: receive, from a source base station, a radio resourcecontrol (RRC) connection reconfiguration message for a random accesschannel-less (RACH-less) handover between the source base station and atarget base station, receive, from the target base station, an uplinkgrant for the RACH-less handover based on the RRC connectionreconfiguration message by monitoring a physical downlink controlchannel (PDCCH), transmit, to the target base station, an RRC connectionreconfiguration complete message for the RACH-less handover based on theuplink grant, the RRC connection reconfiguration complete message beingassociated with a cell radio network temporary identifier (C-RNTI) ofthe terminal, and receive, from the target base station, a medium accesscontrol (MAC) control element (CE) including a contention resolutionidentity of the terminal, as a response to the RRC connectionreconfiguration complete message for completing the RACH-less handover,wherein the MAC CE including the contention resolution identity isreceived based on a physical downlink control channel (PDCCH) addressedto the C-RNTI.
 8. The terminal of claim 7, wherein the controller isfurther configured to control the transceiver to transmit, to the sourcebase station, information indicating that the terminal supports theRACH-less handover.
 9. The terminal of claim 7, wherein the RACH-lesshandover is completed based on the receiving of the MAC CE.
 10. A targetbase station in a wireless communication system, the target base stationcomprising: a transceiver configured to transmit and receive signals;and a controller coupled with the transceiver and configured to:receive, from a source base station, a message requesting a randomaccess channel-less (RACH-less) handover for a terminal, transmit, tothe terminal on a physical downlink control channel (PDCCH), an uplinkgrant for the RACH-less handover based on the message, receive, from theterminal, a radio resource control (RRC) connection reconfigurationcomplete message for the RACH-less handover based on the uplink grant,the RRC connection reconfiguration complete message being associatedwith a cell radio network temporary identifier (C-RNTI) of the terminal,and transmit, to the terminal, a medium access control (MAC) controlelement (CE) including a contention resolution identity of the terminal,as a response to the RRC connection reconfiguration complete message forcompleting the RACH-less handover, wherein the MAC CE including thecontention resolution identity is transmitted based on a physicaldownlink control channel (PDCCH) addressed to the C-RNTI.
 11. The targetbase station of claim 10, wherein information indicating that theterminal supports the RACH-less handover is transmitted from theterminal to the source base station.
 12. The target base station ofclaim 10, wherein the RACH-less handover is completed based on thereceiving of the MAC CE.